846:
1022:
502:
818:
1043:
894:
31:
1316:
2322:(Now I assume that in the case of substances to which a double bond is attributed, actually two affinities of each of the participating atoms are used for their bond; however, on account of the capacity for addition of double bonds, the power of affinity is not completely consumed, and in each of the atoms a remnant of affinity or a "partial valence" exists – an assumption that can also be substantiated thermally .) On p. 90, Thiele coined the term "conjugated":
1354:
1416:
518:
1066:
138:. However, in some cases, more than one Lewis structure could be drawn, and experimental properties are inconsistent with any one structure. In order to address this type of situation, several contributing structures are considered together as an average, and the molecule is said to be represented by a resonance hybrid in which several Lewis structures are used collectively to describe its true structure.
1254:; that of a C=C double bond is 133 pm. In localized cyclohexatriene, the carbon–carbon bonds should be alternating 154 and 133 pm. Instead, all carbon–carbon bonds in benzene are found to be about 139 pm, a bond length intermediate between single and double bond. This mixed single and double bond (or triple bond) character is typical for all molecules in which bonds have a different
367:, a large, whale-like creature. The narwhal is not a creature that goes back and forth between being a unicorn and being a leviathan, nor do the unicorn and leviathan have any physical existence outside the collective human imagination. Nevertheless, describing the narwhal in terms of these imaginary creatures provides a reasonably good description of its physical characteristics.
1232:
142:
1138:. When 1 mole of HCl adds to 1 mole of 1,3-butadiene, in addition to the ordinarily expected product 3-chloro-1-butene, we also find 1-chloro-2-butene. Isotope labelling experiments have shown that what happens here is that the additional double bond shifts from 1,2 position to 2,3 position in some of the product. This and other evidence (such as
675:
One contributing structure may resemble the actual molecule more than another (in the sense of energy and stability). Structures with a low value of potential energy are more stable than those with high values and resemble the actual structure more. The most stable contributing structures are called
768:
Equivalent contributors contribute equally to the actual structure, while the importance of nonequivalent contributors is determined by the extent to which they conform to the properties listed above. A larger number of significant contributing structures and a more voluminous space available for
1637:
group, wherein the negative charge is centered equally on the two oxygen atoms. Charge delocalization in anions is an important factor determining their reactivity (generally: the higher the extent of delocalization the lower the reactivity) and, specifically, the acid strength of their conjugate
1462:
an MO will be delocalized over the whole molecule. This MO interpretation has inspired the picture of the benzene ring as a hexagon with a circle inside. When describing benzene, the VB concept of localized σ bonds and the MO concept of delocalized π orbitals are frequently combined in elementary
1391:
as a linear superposition of the wave functions representing the two structures. As both Kekulé structures have equal energy, they are equal contributors to the overall structure – the superposition is an equally weighted average, or a 1:1 linear combination of the two in the case of benzene. The
2075:
Practicing chemists familiar with the concepts of resonance and delocalization will often draw just one major contributing structure to implicitly represent a molecule whose structure should be described by invoking a resonance hybrid. For example, a chemist might arbitrarily choose to draw the
213:
or delocalization energy. The magnitude of the resonance energy depends on assumptions made about the hypothetical "non-stabilized" species and the computational methods used and does not represent a measurable physical quantity, although comparisons of resonance energies computed under similar
2574:
as well, leading to a higher coordination number for lithium.) Thus, in principle, up to an octet can be accommodated. Nevertheless, the formal number of valence electrons around Li never exceeds two, unless weak donor-acceptor interactions with neutral ligands (e.g., solvent molecules, often
208:
Because electron delocalization lowers the potential energy of a system, any species represented by a resonance hybrid is more stable than any of the (hypothetical) contributing structures. Electron delocalization stabilizes a molecule because the electrons are more evenly spread out over the
1321:
Hydrogenation of one mole of double bonds delivers 119.7 kJ (28.6 kcal), as can be deduced from the last step, the hydrogenation of cyclohexene. In benzene, however, 23.4 kJ (5.6 kcal) are needed to hydrogenate one mole of double bonds. The difference, being 143.1 kJ
740:
Be, B, C, N, O, and F, as is a maximum of two for H and He and effectively for Li as well. The issue of expansion of the valence shell of third period and heavier main group elements is controversial. A Lewis structure in which a central atom has a valence electron count greater than eight
581:
isomers with the brominated carbon atoms joined by either a single or a double bond. In reality there are only three dibromobenzene isomers and only one is ortho, in agreement with the idea that there is only one type of carbon-carbon bond, intermediate between a single and a double bond.
1322:(34.2 kcal), is the empirical resonance energy of benzene. Because 1,3-cyclohexadiene also has a small delocalization energy (7.6 kJ or 1.8 kcal/mol) the net resonance energy, relative to the localized cyclohexatriene, is a bit higher: 151 kJ or 36 kcal/mol.
237:
are molecules with the same chemical formula but are distinct chemical species with different arrangements of atomic nuclei in space. Resonance contributors of a molecule, on the other hand, can only differ in the way electrons are formally assigned to atoms in the Lewis structure
1406:
to find the lowest possible energy for the given set of basis wave functions. When more contributing structures are included, the molecular wave function becomes more accurate and more excited states can be derived from different combinations of the contributing structures.
1146:
solutions) shows that the intermediate carbocation must have a highly delocalized structure, different from its mostly classical (delocalization exists but is small) parent molecule. This cation (an allylic cation) can be represented using resonance, as shown above.
1188:
Delocalized electrons are important for several reasons; a major one is that an expected chemical reaction may not occur because the electrons delocalize to a more stable configuration, resulting in a reaction that happens at a different location. An example is the
251:(a weighted average of the contributors), with a single, well-defined geometry and distribution of electrons. It is incorrect to regard resonance hybrids as rapidly interconverting isomers, even though the term "resonance" might evoke such an image. (As described
2080:
shown on the left, with the understanding that the reader is aware of the other contributor, shown on the right, as well as the implication that the N–O bonds are actually equivalent. This practice is especially prevalent in organic chemistry, where one of the
549:
that are involved in resonance are usually pictured as curves or dashed lines, indicating that these are partial rather than normal complete pi bonds. In benzene and other aromatic rings, the delocalized pi-electrons are sometimes pictured as a solid circle.
1673:
value of −10. The extent of charge delocalization in an anion can be quantitatively expressed via the WAPS (weighted average positive sigma) parameter parameter and an analogous WANS (weighted average negative sigma) parameter is used for cations.
2681:
3085:
Raamat, E.; Kaupmees, K.; Ovsjannikov, G.; Trummal, A.; Kütt, A.; Saame, J.; Koppel, I.; Kaljurand, I.; Lipping, L.; Rodima, T.; Pihl, V.; Koppel, I. A.; Leito, I. (2013). "Acidities of strong neutral Brønsted acids in different media".
1032:
molecule is described by contributing structures, each with electron-deficiency on different atoms. This reduces the electron-deficiency on each atom and stabilizes the molecule. Below are the contributing structures of an individual
2745:
1658:) is evenly distributed among the symmetrically oriented oxygen atoms (and a part of it is also kept by the central chlorine atom). This excellent charge delocalization combined with the high number of oxygen atoms (four) and high
741:
traditionally implies the participation of d orbitals in bonding. However, the consensus opinion is that while they may make a marginal contribution, the participation of d orbitals is unimportant, and the bonding of so-called
181:, ). According to the contributing structures, each N–O bond is an average of a formal single and formal double bond, leading to a true bond order of 1.5. By virtue of this averaging, the Lewis description of the bonding in NO
246:
mean that electrons of the molecule are "resonating" or shifting back and forth between several sets of positions, each one represented by a Lewis structure. Rather, it means that the set of contributing structures
800:, are taken together as contributing structures to represent the total structure. In the hybrid structure on the right, the dashed hexagon replaces three double bonds, and represents six electrons in a set of three
209:
molecule, decreasing electron-electron repulsion. The difference in potential energy between the actual species and the (computed) energy of the contributing structure with the lowest potential energy is called the
761:, for example. Regarded as a formalism that does not necessarily reflect the true electronic structure, such depictions are preferred by the IUPAC over structures featuring partial bonds, charge separation, or
192:
taking on intermediate values compared to those expected for the individual Lewis structures of the contributors, were they to exist as "real" chemical entities. The contributing structures differ only in the
197:
apportionment of electrons to the atoms, and not in the actual physically and chemically significant electron or spin density. While contributing structures may differ in formal bond orders and in
2566:
Li with some degree of covalency, bonding is achieved primarily with the 2s orbital, with some contribution from a 2p orbital. (This bonding scheme is used in condensed phase aggregates like (CH
1387:
For example, in benzene, valence bond theory begins with the two Kekulé structures which do not individually possess the sixfold symmetry of the real molecule. The theory constructs the actual
1258:
in different contributing structures. Bond lengths can be compared using bond orders. For example, in cyclohexane the bond order is 1 while that in benzene is 1 + (3 ÷ 6) =
255:, the term "resonance" originated as a classical physics analogy for a quantum mechanical phenomenon, so it should not be construed too literally.) Symbolically, the double headed arrow
1366:
1345:
are, respectively, 88, 121, and 67 kJ/mol (21, 29, and 16 kcal/mol). Thus, these heterocycles are far less aromatic than benzene, as is manifested in the lability of these rings.
904:, the rationalization described above can be applied to generate contributing structures to explain the bonding in such molecules. Shown below are the contributing structures of a
346:
2330:(Such a system of adjacent double bonds with equalized inner partial valences shall be termed "conjugated".) Thiele discussed the conjugated structure of benzene on pp. 125–129:
281:
1384:(VB). Quantum mechanics requires that the wavefunction of a molecule obey its observed symmetry. If a single contributing structure does not achieve this, resonance is invoked.
861:
molecule is represented by two contributing structures. In reality the two terminal oxygen atoms are equivalent and the hybrid structure is drawn on the right with a charge of −
3429:
126:, and connected by bonds of positive integer order, is sufficient for describing the chemical bonding and rationalizing experimentally determined molecular properties like
1185:
and are represented either by contributing structures involving rearrangement of σ electrons or by a special notation, a Y that has the three nuclei at its three points.
1280:
Resonance (or delocalization) energy is the amount of energy needed to convert the true delocalized structure into that of the most stable contributing structure. The
986:
483:
217:
Molecules with an extended π system such as linear polyenes and polyaromatic compounds are well described by resonance hybrids as well as by delocalised orbitals in
1325:
This measured resonance energy is also the difference between the hydrogenation energy of three 'non-resonance' double bonds and the measured hydrogenation energy:
390:. The double headed arrows would be replaced by commas to illustrate a set of structures, as arrows of any type may suggest that a chemical change is taking place.
2802:
636:
for two decades thanks to being relatively easier to understand for chemists without fundamental physics background, even if they couldn't grasp the concept of
566:'s structure proposed in 1865 with alternating single and double bonds. Benzene undergoes substitution reactions, rather than addition reactions as typical for
593:
in 1926 in a discussion of the quantum states of the helium atom. He compared the structure of the helium atom with the classical system of resonating coupled
149:, shown on the right, is best rationalized by describing its structure as a resonance hybrid consisting of two major and equally important contributing forms.
655:
In the Soviet Union, resonance theory – especially as developed by
Pauling – was attacked in the early 1950s as being contrary to the Marxist principles of
534:
In diagrams, contributing structures are typically separated by double-headed arrows (↔). The arrow should not be confused with the right and left pointing
2943:
Kaupmees, K.; Kaljurand, I.; Leito, I. (2010). "Influence of Water
Content on the Acidities in Acetonitrile. Quantifying Charge Delocalization in Anions".
2402:
605:
used this mechanism to explain the partial valence of molecules in 1928, and developed it further in a series of papers in 1931-1933. The alternative term
1478:
on benzene. The utility of MO theory is that a quantitative indication of the charge from the π system on an atom can be obtained from the squares of the
165:. However, its measured structure is consistent with a description as a resonance hybrid of the two major contributing structures shown above: it has two
1633:
In the case of ions it is common to speak about delocalized charge (charge delocalization). An example of delocalized charge in ions can be found in the
716:
do not deviate substantially from idealized bond lengths and angles (e.g., the relative unimportance of Dewar-type resonance contributors for benzene);
538:(⇌). All structures together may be enclosed in large square brackets, to indicate they picture one single molecule or ion, not different species in a
102:. The resonance hybrid is the accurate structure for a molecule or ion; it is an average of the theoretical (or hypothetical) contributing structures.
3130:
2468:
2151:
2014:
1985:
1333:
Regardless of their exact values, resonance energies of various related compounds provide insights into their bonding. The resonance energies for
1452:
that indicates the AO's contribution to a particular MO. For example, in benzene, the MO model gives us 6 π MOs which are combinations of the 2p
1621:, or finally from empirical calculations based on the Hückel method. A Hückel method-based software for teaching resonance is available on the
1780:
1602:
Weighting of the contributing structures in terms of their contribution to the overall structure can be calculated in multiple ways, using
703:
663:
convened a conference on the chemical structure of organic compounds, attended by 400 physicists, chemists, and philosophers, where "the
2372:
573:
The resonance proposal also helped explain the number of isomers of benzene derivatives. For example, Kekulé's structure would predict
797:
3465:
3436:
17:
2345:
283:
is used to indicate that A and B are contributing forms of a single chemical species (as opposed to an equilibrium arrow, e.g.,
1087:
1006:
has two contributing structures with a positive charge on the terminal carbon atoms. In the hybrid structure their charge is +
3617:
3368:
3123:
2916:
2891:
2859:
2136:
2108:
1432:
118:
can be described by a Lewis structure. For many chemical species, a single Lewis structure, consisting of atoms obeying the
1516:. The reason for squaring the coefficient is that if an electron is described by an AO, then the square of the AO gives the
3472:
2388:
188:
The resonance hybrid represents the actual molecule as the "average" of the contributing structures, with bond lengths and
1134:
have more delocalized structure than their parent reactants, giving rise to unexpected products. The classical example is
2830:
2657:
545:
Alternatively to the use of contributing structures in diagrams, a hybrid structure can be used. In a hybrid structure,
374:, as no entities actually physically "resonate", it has been suggested that the term resonance be abandoned in favor of
161:
anion, the two N–O bond lengths are equal, even though no single Lewis structure has two N–O bonds with the same formal
2060:
1150:
This observation of greater delocalization in less stable molecules is quite general. The excited states of conjugated
845:
1928:
601:
than either of the uncoupled vibrations; quantum mechanically, this lower frequency is interpreted as a lower energy.
3539:
3161:
2355:
1113:
1095:
242:
of the molecule. Specifically, when a molecular structure is said to be represented by a resonance hybrid, it does
3116:
2441:
Pauling, Linus. (1931). "The Nature of the
Chemical Bond. Ii. The One-Electron Bond and the Three-Electron Bond".
1042:
1021:
2907:
Sellers, Kathleen; Weeks, Katherine; Alsop, William R.; Clough, Stephen R.; Hoyt, Marilyn; Pugh, Barbara (2006).
905:
746:
3513:
1182:
1091:
1034:
684:. With rules listed in rough order of diminishing importance, major contributors are generally structures that
1458:
AOs on each of the 6 C atoms. Thus, each π MO is delocalized over the whole benzene molecule and any electron
3571:
3399:
2293:
2181:
1729:
1614:
1272:. Consequently, benzene has more double bond character and hence has a shorter bond length than cyclohexane.
749:. Nevertheless, by tradition, expanded octet structures are still commonly drawn for functional groups like
562:'s "Partial Valence Hypothesis" to explain the unusual stability of benzene which would not be expected from
3001:
Kaupmees, K.; Kaljurand, I.; Leito, I. (2014). "Influence of Water
Content on Basicities in Acetonitrile".
617:
has taken on a related but different meaning. The double headed arrow was introduced by the German chemist
286:
201:
assignments, all contributing structures must have the same number of valence electrons and the same spin
3612:
2849:
1800:
1190:
817:
258:
1566:
1471:
1403:
578:
745:
molecules are, for the most part, better explained by charge-separated contributing forms that depict
3607:
3389:
3373:
692:(8 valence electrons around each atom rather than having deficiencies or surplus, or 2 electrons for
652:
sent him a friendly request, he responded arrogantly that he is not interested in organic chemistry.
649:
559:
2324:"Ein solches System benachbarter Doppelbindungen mit ausgeglichenen inneren Partialvalenzen sei als
2267:
2242:
1242:
Comparing the two contributing structures of benzene, all single and double bonds are interchanged.
893:
3348:
2883:
1591:
1475:
1424:
1076:
762:
355:
A non-chemical analogy is illustrative: one can describe the characteristics of a real animal, the
218:
202:
1392:
symmetric combination gives the ground state, while the antisymmetric combination gives the first
1154:
are stabilised more by conjugation than their ground states, causing them to become organic dyes.
570:. He proposed that the carbon-carbon bond in benzene is intermediate of a single and double bond.
3534:
2587:"Graphical representation standards for chemical structure diagrams (IUPAC Recommendations 2008)"
1080:
664:
656:
610:
1466:
The contributing structures in the VB model are particularly useful in predicting the effect of
648:'s approach as "cumbersome" at the time, and his lack of communication skills contributed: when
3422:
1638:
acids. As a general rule, the better delocalized is the charge in an anion the stronger is its
2426:
3501:
3303:
2048:
1400:
1135:
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918:
637:
402:
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95:
1958:"HuLiS : Java Applet − Simple Hückel Theory and Mesomery − program logiciel software"
8:
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3496:
3394:
3288:
2876:
2550:
Terror and
Progress USSR: Some Sources of Change and Stability in the Soviet Dictatorship
1820:
1428:
1381:
1016:. The full positive charge can also be depicted as delocalized among three carbon atoms.
997:
594:
169:
N–O bonds of 125 pm, intermediate in length between a typical N–O single bond (145 pm in
111:
91:
2956:
2220:
1470:
on π systems such as benzene. They lead to the models of contributing structures for an
1399:
In general, the superposition is written with undetermined coefficients, which are then
706:, with the separation for unlike and like charges minimized and maximized, respectively;
3561:
3518:
3018:
2822:
2707:
2527:
2519:
1938:
1719:
1373:
1300:
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135:
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delocalized electrons lead to stabilization (lowering of the energy) of the molecule.
3555:
3363:
3156:
2968:
2912:
2887:
2855:
2727:
2608:
2562:
Lithium is always found as Li (1s), a duet, in ionic compounds. In compounds like CH
2531:
2419:
2396:
2351:
2132:
2104:
2056:
1933:
1912:
1892:
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801:
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597:. In the classical system, the coupling produces two modes, one of which is lower in
590:
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3022:
2826:
2478:
2161:
2024:
1995:
3095:
3056:
3010:
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2814:
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2719:
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2511:
2500:"The Technology: Science Interaction: Walter Reppe and Cyclooctatetraene Chemistry"
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2019:
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1943:
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115:
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popular in German and French publications with the same meaning was introduced by
563:
501:
185:
is reconciled with the experimental fact that the anion has equivalent N–O bonds.
3313:
2498:
Morris, Peter J. T.; Hornix, Willem J.; Bud, Robert; Morris, Peter J. T. (1992).
1856:
1839:
1678:
WAPS values of anions of common acids and WANS values of cations of common bases
1663:
1618:
1285:
758:
488:
99:
63:
2746:"4.10: Alkylation and Acylation of Aromatic Rings - The Friedel-Crafts Reaction"
2436:
2053:
The Nature of the
Chemical Bond – An Introduction to Modern Structural Chemistry
645:
613:
in 1938, but did not catch on in the
English literature. The current concept of
3256:
3240:
3235:
3151:
2432:
2089:
is frequently chosen to depict the regular hexagonal structure of the molecule.
1761:
1639:
809:
723:
189:
3014:
2515:
871:
on both oxygen atoms and partial double bonds with a full and dashed line and
27:
Description of a molecule's true bond structure as a combination of structures
3601:
3445:
3329:
3269:
3264:
3245:
3139:
2731:
2612:
2477:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
2309:
2160:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
2023:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
1994:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
1916:
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602:
198:
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123:
55:
30:
2603:
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The resonance hybrid is more stable than any of the contributing structures.
2032:
2003:
1157:
A well-studied example of delocalization that does not involve π electrons (
3586:
2972:
1791:
1467:
1127:
1003:
833:
719:
maintain aromatic substructures locally while avoiding anti-aromatic ones (
3108:
1292:
of the real substance with that estimated for the contributing structure.
832:
of the oxygen atom interacts with the π orbitals of the carbon atoms. The
659:, and in June 1951 the Soviet Academy of Sciences under the leadership of
3230:
3225:
3220:
2845:
2082:
1919:. Larger values indicate more localized charge in the corresponding ion.
1900:
1831:
1753:
1643:
1634:
1304:
1296:
1243:
1197:
783:
729:
680:. Energetically unfavourable and therefore less favorable structures are
641:
618:
131:
127:
2787:
2454:
1315:
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3186:
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2499:
1308:
1255:
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1193:
872:
805:
689:
162:
119:
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2320:
vorhanden ist, eine
Annahme, die sich auch thermisch begründen lässt."
2228:
1955:
3334:
3099:
2723:
1956:
Goudard, N.; Carissan, Y.; Hagebaum-Reignier, D.; Humbel, S. (2008).
1415:
1380:
Resonance has a deeper significance in the mathematical formalism of
1353:
1338:
1166:
1143:
829:
750:
598:
371:
364:
59:
43:
35:
3061:
3044:
2207:
Kerber, Robert C. (2006). "If It's
Resonance, What Is Resonating?".
1065:
3201:
1864:
1029:
546:
1365:
labels define the symmetries of the two states, as defined by the
3191:
2086:
1882:
1611:
1334:
1236:
1221:
789:
754:
524:
517:
508:
360:
359:, in terms of the characteristics of two mythical creatures: the
356:
158:
3414:
3084:
2851:
Advanced
Organic Chemistry: Reactions, Mechanisms, and Structure
1410:
2314:
On p. 89, Thiele introduced the concept of "partial valence":
1811:
713:
atoms and positive charge, if any, on the most electropositive;
567:
234:
230:
667:
essence of the theory of resonance was exposed and unmasked".
114:, resonance is an extension of the idea that the bonding in a
2843:
2278:
2253:
1435:(AOs) on all the atoms; there are as many MOs as AOs. Each AO
1342:
1311:; 1 mole of benzene delivers 208.4 kJ (49.8 kcal).
1205:
1151:
858:
825:
3045:"Basicities of Strong Bases in Water: A Computational Study"
2770:
Wiberg; Nakaji; Morgan (1993). "Heat of hydrogenation of a
2129:
Advanced Organic Chemistry Part A: Structure and Mechanisms
1957:
1622:
1606:
methods derived from Valence Bond theory, or else from the
2854:(6th ed.), New York: Wiley-Interscience, p. 62,
2268:"Graphical representation for chemical structure diagrams"
2243:"Graphical representation for chemical structure diagrams"
2055:(3rd ed.). Cornell University Press. pp. 10–13.
1349:
Quantum mechanical description in valence bond (VB) theory
141:
2431:
In this source, Pauling first mentions related papers by
1139:
214:
assumptions and conditions may be chemically meaningful.
2803:"The heats of hydrogenation of unsaturated hydrocarbons"
1231:
2906:
1329:(3 × 119.7) − 208.4 = 150.7 kJ/mol (36 kcal).
736:
A maximum of eight valence electrons is strict for the
370:
Due to confusion with the physical meaning of the word
3000:
2942:
2296:[ to our knowledge of unsaturated compounds].
315:
2497:
2103:(5th ed.). Prentice Hall of India. p. 372.
2099:
Morrison, Robert; Boyd, Robert (1989). "Chapter 10".
921:
405:
363:, a creature with a single horn on its head, and the
289:
261:
3042:
98:
where the bonding cannot be expressed by one single
1431:, the molecular orbitals (MOs) are approximated as
2769:
2418:
2350:(2nd ed.). Thomson Learning. pp. 470–1.
2332:VIII. Die aromatischen Verbindungen. Das Benzol.
980:
477:
340:
275:
145:The experimental geometry of the nitrite anion, NO
2909:Perchlorate: Environmental problems and solutions
2425:(3rd ed.). Oxford University Press. p.
1250:. The average length of a C–C single bond is 154
450:
323:
322:
305:
304:
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2401:: CS1 maint: bot: original URL status unknown (
2127:Carey, Francis A.; Sundberg, Richard J. (2007).
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2984:
2982:
2774:imine. An experimental and theoretical study".
2145:
1666:being one of the strongest known acids with a p
991:
670:
644:. Pauling and Wheland themselves characterized
585:The mechanism of resonance was introduced into
349:
2874:Shaik, Sason S.; Hiberty, Phillipe C. (2008).
2504:The British Journal for the History of Science
1196:of benzene with 1-chloro-2-methylpropane; the
3430:
3124:
3043:Kaupmees, K.; Trummal, A.; Leito, I. (2014).
2294:"Zur Kenntnis der ungesättigten Verbindungen"
2126:
1411:Comparison with molecular orbital (MO) theory
393:
3029:
2979:
2873:
2575:omitted from Lewis structures) are included.
2439:in 1931, and then cites his own key papers:
2098:
3138:
2938:
2936:
2934:
2932:
2930:
2928:
2882:. New Jersey: Wiley-Interscience. pp.
2391:. Archived from the original on 2012-03-31.
2389:"The Science and Humanism of Linus Pauling"
2008:
1094:. Unsourced material may be challenged and
840:, which results in different contributors.
709:place negative charge, if any, on the most
378:and resonance energy abandoned in favor of
3437:
3423:
3131:
3117:
2655:
2462:
2334:(VIII. The aromatic compounds. Benzene.)
852:
632:Resonance theory dominated over competing
3080:
3078:
3076:
3074:
3072:
3060:
2900:
2708:"The 2-norbornyl cation: a retrospective"
2602:
2042:
2040:
1295:The complete hydrogenation of benzene to
1114:Learn how and when to remove this message
1049:
968:
960:
951:
938:
929:
224:
2925:
2878:A Chemist's Guide to Valence Bond Theory
2343:
1979:
1628:
1414:
1352:
1230:
699:have a maximum number of covalent bonds;
140:
94:. It has particular value for analyzing
29:
3466:Sickle Cell Anemia, a Molecular Disease
2800:
2584:
2440:
2416:
2046:
1565: = 1 on each C atom. With an
1212:, a particular form of delocalization.
1161:) can be observed in the non-classical
298:
14:
3600:
3069:
2682:"16.12 Conjugated Dienes and UV Light"
2291:
2206:
2037:
1662:of the central chlorine atom leads to
1642:. For example, the negative charge in
1126:Often, reactive intermediates such as
964:
955:
942:
933:
577:dibromobenzene isomers, including two
558:The concept first appeared in 1899 in
229:Resonance is to be distinguished from
3418:
3112:
2712:Journal of Physical Organic Chemistry
2658:"Bonus Topic: Allylic Rearrangements"
2544:
1181:). These can be viewed as containing
777:
386:and the resonance hybrid becomes the
341:{\displaystyle {\ce {A <=> B}}}
177:N–OH) and N–O double bond (115 pm in
2705:
1092:adding citations to reliable sources
1059:
249:represents an intermediate structure
2706:Moss, Robert A. (4 February 2014).
2370:
1357:VB mixing diagram of benzene. The A
1275:
1246:can be measured, for example using
276:{\displaystyle {\ce {A<->B}}}
24:
3480:How to Live Longer and Feel Better
2640:
2474:Compendium of Chemical Terminology
2298:Justus Liebig's Annalen der Chemie
2157:Compendium of Chemical Terminology
2020:Compendium of Chemical Terminology
1991:Compendium of Chemical Terminology
1911:WAPS and WANS values are given in
1284:can be estimated by comparing the
747:three-center four-electron bonding
382:. A resonance structure becomes a
25:
3629:
3540:International League of Humanists
3444:
3162:Introduction to quantum mechanics
2734:– via Wiley Online Library.
2459:and subsequent papers in 1932–33.
1949:
704:minimum of formally charged atoms
2656:Ashenhurst, James (2013-12-02).
2625:
2585:Brecher, Jonathan (2008-01-01).
2407:See last paragraph of section 1.
1524:) so that AO = 1, and
1314:
1064:
1041:
1020:
892:
844:
816:
621:who preferred the German phrase
516:
500:
3514:Pauling Electronegativity Scale
3460:The Nature of the Chemical Bond
2867:
2837:
2794:
2763:
2738:
2699:
2674:
2649:
2634:
2619:
2578:
2556:
2538:
2491:
2421:The Nature of the Chemical Bond
2410:
2381:
2364:
2337:
2285:
2260:
2235:
1929:Hückel molecular orbital theory
1597:
1433:sums of all the atomic orbitals
1419:π molecular orbitals of benzene
1226:
1183:three-center two-electron bonds
487:Contributing structures of the
34:Contributing structures of the
2200:
2174:
2120:
2092:
2069:
973:
947:
924:
812:in the plane of the molecule.
796:structures, first proposed by
491:, enclosed in square brackets.
470:
437:
408:
325:
300:
266:
66:by the combination of several
13:
1:
3473:Vitamin C and the Common Cold
2801:Sherman, J. (February 1939).
1973:
1610:(NBO) approaches of Weinhold
688:obey as much as possible the
3618:Electronic structure methods
2344:Hornback, Joseph M. (2006).
2316:"Ich nehme nun an, ... eine
1781:7-Methyl-triazabicyclodecene
1745:Phenyl tetramethylguanidine
992:Electron-deficient molecules
671:Major and minor contributors
252:
7:
2076:resonance contributor of NO
1922:
1801:1,8-Diazabicycloundec-7-ene
1676:
1235:Contributing structures of
772:
105:
10:
3634:
2591:Pure and Applied Chemistry
2275:IUPAC Recommendations 2008
2250:IUPAC Recommendations 2008
2049:"The Concept of Resonance"
1567:electron-withdrawing group
1472:electron-withdrawing group
1427:, the main alternative to
1282:empirical resonance energy
1219:
1215:
1053:
995:
836:depict the permutation of
781:
553:
394:Representation in diagrams
74:, also variously known as
3572:Intravenous ascorbic acid
3548:
3527:
3489:
3452:
3382:
3356:
3347:
3322:
3296:
3287:
3254:
3210:
3179:
3172:
3147:
3015:10.1007/s10953-014-0201-4
2911:. CRC Press. p. 16.
2516:10.1017/S0007087400045374
2292:Thiele, Johannes (1899).
2281:, pp. 379–382 (GR–6)
1590: > 1 for an
1575: < 1 on the
54:, is a way of describing
3349:Molecular orbital theory
2662:Master Organic Chemistry
2310:10.1002/jlac.18993060107
2131:. Springer. p. 19.
1592:electron-releasing group
1520:. The AOs are adjusted (
1476:electron-releasing group
1425:molecular orbital theory
981:{\displaystyle {\ce {}}}
792:the two cyclohexatriene
507:Hybrid structure of the
478:{\displaystyle {\ce {}}}
219:molecular orbital theory
3535:Linus Pauling Institute
2604:10.1351/pac200880020277
2487:10.1351/goldbook.M03845
2170:10.1351/goldbook.R05333
2047:Pauling, Linus (1960).
2033:10.1351/goldbook.C01309
2004:10.1351/goldbook.R05326
853:Electron-rich molecules
838:delocalized π electrons
657:dialectical materialism
352:for details on usage).
110:Under the framework of
68:contributing structures
18:Resonance stabilization
2025:contributing structure
1420:
1377:
1239:
1050:Reactive intermediates
982:
479:
384:contributing structure
342:
277:
225:Resonance vs isomerism
150:
39:
3502:Orbital hybridisation
2546:Moore, Barrington Jr.
2188:. UCDavis. 2013-10-02
1629:Charge delocalization
1608:Natural Bond Orbitals
1418:
1356:
1234:
1136:allylic rearrangement
1056:Reactive intermediate
983:
902:hypervalent molecules
640:and confused it with
638:quantum superposition
480:
380:delocalization energy
343:
278:
144:
96:delocalized electrons
33:
3567:Vitamin C megadosage
2807:J. Am. Oil Chem. Soc
2750:Chemistry LibreTexts
2686:Chemistry LibreTexts
2417:Pauling, L. (1960).
2256:, p. 387 (GR–8)
1692:WANS × 10
1686:WAPS × 10
1208:group stabilized by
1088:improve this section
919:
661:Alexander Nesmeyanov
595:harmonic oscillators
540:chemical equilibrium
523:Hybrid structure of
403:
287:
259:
80:canonical structures
76:resonance structures
3577:Linus Pauling Award
3497:Valence bond theory
3289:Valence bond theory
2957:2010JPCA..11411788K
2951:(43): 11788–11793.
2844:Smith, Michael B.;
2788:10.1021/ja00062a017
2552:. pp. 142–143.
2455:10.1021/ja01360a004
2221:2006JChEd..83..223K
1821:Triazabicyclodecene
1679:
1463:chemistry courses.
1429:valence bond theory
1382:valence bond theory
1165:Another example is
998:Electron deficiency
311:
153:For instance, in NO
122:, possibly bearing
112:valence bond theory
92:valence bond theory
3613:Physical chemistry
3562:Molecular medicine
3088:J. Phys. Org. Chem
2819:10.1007/BF02543208
1939:Fluxional molecule
1720:Triphenylphosphine
1677:
1617:2008-02-08 at the
1421:
1378:
1301:1,3-cyclohexadiene
1240:
1163:2-Norbornyl cation
1037:bond in diborane.
978:
802:molecular orbitals
778:Aromatic molecules
682:minor contributors
678:major contributors
627:intermediate stage
475:
338:
330:
273:
151:
40:
3595:
3594:
3556:Ava Helen Pauling
3412:
3411:
3408:
3407:
3383:Constituent units
3364:Molecular orbital
3343:
3342:
3323:Constituent units
3283:
3282:
3157:Quantum mechanics
3049:Croat. Chem. Acta
2965:10.1021/jp105670t
2918:978-0-8493-8081-5
2893:978-0-470-03735-5
2861:978-0-471-72091-1
2643:Organic Chemistry
2641:Bruice, Paula Y.
2628:Organic Chemistry
2347:Organic Chemistry
2229:10.1021/ed083p223
2186:UCDavis Chem Wiki
2182:"Resonance Forms"
2138:978-0-387-68346-1
2110:978-0-87692-560-7
2101:Organic Chemistry
2083:Kekulé structures
1934:Conjugated system
1909:
1908:
1772:2,4-Dinitrophenol
1660:electronegativity
1248:X-ray diffraction
1124:
1123:
1116:
970:
962:
953:
940:
931:
808:symmetry, with a
759:phosphorus ylides
738:Period 2 elements
694:Period 1 elements
665:pseudo-scientific
591:Werner Heisenberg
587:quantum mechanics
536:equilibrium arrow
469:
461:
453:
443:
430:
421:
413:
336:
332:
293:
271:
265:
16:(Redirected from
3625:
3608:Chemical bonding
3439:
3432:
3425:
3416:
3415:
3354:
3353:
3294:
3293:
3275:Exchange-coupled
3177:
3176:
3140:Chemical bonding
3133:
3126:
3119:
3110:
3109:
3104:
3103:
3100:10.1002/poc.2946
3082:
3067:
3066:
3064:
3040:
3027:
3026:
3009:(7): 1270–1281.
2998:
2977:
2976:
2945:J. Phys. Chem. A
2940:
2923:
2922:
2904:
2898:
2897:
2881:
2871:
2865:
2864:
2841:
2835:
2834:
2829:. Archived from
2798:
2792:
2791:
2782:(9): 3527–3532.
2776:J. Am. Chem. Soc
2767:
2761:
2760:
2758:
2757:
2742:
2736:
2735:
2724:10.1002/poc.3290
2703:
2697:
2696:
2694:
2693:
2678:
2672:
2671:
2669:
2668:
2653:
2647:
2646:
2638:
2632:
2631:
2623:
2617:
2616:
2606:
2582:
2576:
2560:
2554:
2553:
2542:
2536:
2535:
2495:
2489:
2466:
2460:
2458:
2443:J. Am. Chem. Soc
2430:
2424:
2414:
2408:
2406:
2400:
2392:
2385:
2379:
2378:
2371:Pauling, Linus,
2368:
2362:
2361:
2341:
2335:
2313:
2289:
2283:
2282:
2272:
2264:
2258:
2257:
2247:
2239:
2233:
2232:
2204:
2198:
2197:
2195:
2193:
2178:
2172:
2162:resonance energy
2149:
2143:
2142:
2124:
2118:
2117:
2096:
2090:
2073:
2067:
2066:
2044:
2035:
2012:
2006:
1983:
1969:
1967:
1965:
1944:Avoided crossing
1847:-Dimethylaniline
1680:
1657:
1656:
1655:
1557:
1556:
1518:electron density
1515:
1514:
1318:
1276:Resonance energy
1271:
1270:
1266:
1263:
1210:hyperconjugation
1200:rearranges to a
1180:
1179:
1178:
1159:hyperconjugation
1119:
1112:
1108:
1105:
1099:
1068:
1060:
1045:
1024:
1015:
1014:
1010:
987:
985:
984:
979:
977:
976:
972:
971:
967:
959:
958:
946:
945:
936:
910:xenon difluoride
896:
887:
886:
882:
879:
870:
869:
865:
848:
820:
615:mesomeric effect
520:
504:
484:
482:
481:
476:
474:
473:
467:
466:
459:
458:
451:
449:
448:
441:
436:
435:
428:
426:
419:
418:
411:
388:hybrid structure
347:
345:
344:
339:
337:
334:
333:
331:
329:
328:
321:
313:
312:
310:
303:
295:
291:
282:
280:
279:
274:
272:
269:
263:
211:resonance energy
116:chemical species
88:hybrid structure
84:resonance hybrid
21:
3633:
3632:
3628:
3627:
3626:
3624:
3623:
3622:
3598:
3597:
3596:
3591:
3544:
3523:
3519:Pauling's rules
3485:
3448:
3443:
3413:
3404:
3378:
3339:
3318:
3314:Lewis structure
3279:
3250:
3206:
3168:
3143:
3137:
3107:
3083:
3070:
3062:10.5562/cca2472
3041:
3030:
2999:
2980:
2941:
2926:
2919:
2905:
2901:
2894:
2872:
2868:
2862:
2842:
2838:
2799:
2795:
2768:
2764:
2755:
2753:
2744:
2743:
2739:
2704:
2700:
2691:
2689:
2680:
2679:
2675:
2666:
2664:
2654:
2650:
2645:(4th ed.).
2639:
2635:
2630:(6th ed.).
2624:
2620:
2583:
2579:
2573:
2569:
2565:
2561:
2557:
2543:
2539:
2496:
2492:
2467:
2463:
2415:
2411:
2394:
2393:
2387:
2386:
2382:
2369:
2365:
2358:
2342:
2338:
2290:
2286:
2270:
2266:
2265:
2261:
2245:
2241:
2240:
2236:
2205:
2201:
2191:
2189:
2180:
2179:
2175:
2150:
2146:
2139:
2125:
2121:
2111:
2097:
2093:
2079:
2074:
2070:
2063:
2045:
2038:
2013:
2009:
1984:
1980:
1976:
1963:
1961:
1952:
1925:
1737:
1733:
1712:
1708:
1704:
1700:
1672:
1664:perchloric acid
1654:
1651:
1650:
1649:
1647:
1631:
1619:Wayback Machine
1600:
1588:
1573:
1563:
1555:
1550:
1549:
1548:
1543:
1536:
1529:
1513:
1508:
1507:
1506:
1500:
1494:
1487:
1457:
1450:
1440:
1413:
1372:
1367:character table
1364:
1360:
1351:
1286:enthalpy change
1278:
1268:
1264:
1261:
1259:
1229:
1224:
1218:
1177:
1174:
1173:
1172:
1170:
1120:
1109:
1103:
1100:
1085:
1069:
1058:
1052:
1012:
1008:
1007:
1000:
994:
963:
954:
950:
941:
937:
932:
928:
927:
923:
922:
920:
917:
916:
884:
880:
877:
875:
867:
863:
862:
855:
786:
780:
775:
711:electronegative
673:
650:Robert Robinson
560:Johannes Thiele
556:
532:
531:
530:
529:
528:
521:
513:
512:
505:
494:
493:
492:
489:thiocyanate ion
485:
462:
454:
444:
440:
431:
427:
422:
414:
407:
406:
404:
401:
400:
396:
324:
317:
316:
314:
306:
299:
297:
296:
294:
290:
288:
285:
284:
262:
260:
257:
256:
227:
190:partial charges
184:
176:
156:
148:
108:
100:Lewis structure
64:polyatomic ions
28:
23:
22:
15:
12:
11:
5:
3631:
3621:
3620:
3615:
3610:
3593:
3592:
3590:
3589:
3584:
3579:
3574:
3569:
3564:
3559:
3552:
3550:
3546:
3545:
3543:
3542:
3537:
3531:
3529:
3525:
3524:
3522:
3521:
3516:
3511:
3510:
3509:
3504:
3493:
3491:
3487:
3486:
3484:
3483:
3477:
3469:
3463:
3456:
3454:
3450:
3449:
3442:
3441:
3434:
3427:
3419:
3410:
3409:
3406:
3405:
3403:
3402:
3400:Antibonding MO
3397:
3395:Non-bonding MO
3392:
3386:
3384:
3380:
3379:
3377:
3376:
3371:
3366:
3360:
3358:
3351:
3345:
3344:
3341:
3340:
3338:
3337:
3332:
3326:
3324:
3320:
3319:
3317:
3316:
3311:
3306:
3304:Hybrid orbital
3300:
3298:
3291:
3285:
3284:
3281:
3280:
3278:
3277:
3272:
3267:
3261:
3259:
3252:
3251:
3249:
3248:
3243:
3238:
3233:
3228:
3223:
3217:
3215:
3208:
3207:
3205:
3204:
3199:
3194:
3189:
3183:
3181:
3174:
3173:Types of bonds
3170:
3169:
3167:
3166:
3165:
3164:
3154:
3152:Atomic orbital
3148:
3145:
3144:
3136:
3135:
3128:
3121:
3113:
3106:
3105:
3094:(2): 162–170.
3068:
3055:(4): 385–395.
3028:
3003:J. Solut. Chem
2978:
2924:
2917:
2899:
2892:
2866:
2860:
2836:
2833:on 2011-07-14.
2793:
2762:
2737:
2718:(5): 374–379.
2698:
2673:
2648:
2633:
2618:
2597:(2): 277–410.
2577:
2571:
2567:
2563:
2555:
2537:
2510:(1): 145–167.
2490:
2461:
2449:(1367): 3225.
2409:
2380:
2363:
2356:
2336:
2284:
2259:
2234:
2199:
2173:
2144:
2137:
2119:
2109:
2091:
2077:
2068:
2062:978-0801403330
2061:
2036:
2007:
1977:
1975:
1972:
1971:
1970:
1951:
1950:External links
1948:
1947:
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1941:
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1764:
1762:Tripropylamine
1759:
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1725:
1722:
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1710:
1706:
1702:
1698:
1694:
1693:
1690:
1687:
1684:
1670:
1652:
1640:conjugate acid
1630:
1627:
1599:
1596:
1586:
1571:
1561:
1558:. In benzene,
1551:
1539:
1534:
1531: ≈ (
1527:
1509:
1498:
1490:
1485:
1453:
1448:
1436:
1412:
1409:
1370:
1362:
1358:
1350:
1347:
1331:
1330:
1277:
1274:
1228:
1225:
1220:Main article:
1217:
1214:
1191:Friedel–Crafts
1175:
1122:
1121:
1072:
1070:
1063:
1054:Main article:
1051:
1048:
1047:
1046:
1026:
1025:
996:Main article:
993:
990:
989:
988:
975:
966:
957:
949:
944:
935:
926:
898:
897:
854:
851:
850:
849:
822:
821:
782:Main article:
779:
776:
774:
771:
734:
733:
717:
714:
707:
700:
697:
672:
669:
555:
552:
522:
515:
514:
506:
499:
498:
497:
496:
495:
486:
472:
465:
457:
447:
439:
434:
425:
417:
410:
399:
398:
397:
395:
392:
376:delocalization
327:
320:
309:
302:
268:
226:
223:
182:
174:
154:
146:
124:formal charges
107:
104:
50:, also called
26:
9:
6:
4:
3:
2:
3630:
3619:
3616:
3614:
3611:
3609:
3606:
3605:
3603:
3588:
3585:
3583:
3582:Pauling Field
3580:
3578:
3575:
3573:
3570:
3568:
3565:
3563:
3560:
3557:
3554:
3553:
3551:
3547:
3541:
3538:
3536:
3533:
3532:
3530:
3526:
3520:
3517:
3515:
3512:
3508:
3505:
3503:
3500:
3499:
3498:
3495:
3494:
3492:
3488:
3481:
3478:
3475:
3474:
3470:
3467:
3464:
3461:
3458:
3457:
3455:
3451:
3447:
3446:Linus Pauling
3440:
3435:
3433:
3428:
3426:
3421:
3420:
3417:
3401:
3398:
3396:
3393:
3391:
3388:
3387:
3385:
3381:
3375:
3372:
3370:
3367:
3365:
3362:
3361:
3359:
3355:
3352:
3350:
3346:
3336:
3333:
3331:
3330:Covalent bond
3328:
3327:
3325:
3321:
3315:
3312:
3310:
3307:
3305:
3302:
3301:
3299:
3295:
3292:
3290:
3286:
3276:
3273:
3271:
3268:
3266:
3263:
3262:
3260:
3258:
3253:
3247:
3244:
3242:
3241:5 (quintuple)
3239:
3237:
3236:4 (quadruple)
3234:
3232:
3229:
3227:
3224:
3222:
3219:
3218:
3216:
3214:
3209:
3203:
3200:
3198:
3195:
3193:
3190:
3188:
3185:
3184:
3182:
3178:
3175:
3171:
3163:
3160:
3159:
3158:
3155:
3153:
3150:
3149:
3146:
3141:
3134:
3129:
3127:
3122:
3120:
3115:
3114:
3111:
3101:
3097:
3093:
3089:
3081:
3079:
3077:
3075:
3073:
3063:
3058:
3054:
3050:
3046:
3039:
3037:
3035:
3033:
3024:
3020:
3016:
3012:
3008:
3004:
2997:
2995:
2993:
2991:
2989:
2987:
2985:
2983:
2974:
2970:
2966:
2962:
2958:
2954:
2950:
2946:
2939:
2937:
2935:
2933:
2931:
2929:
2920:
2914:
2910:
2903:
2895:
2889:
2885:
2880:
2879:
2870:
2863:
2857:
2853:
2852:
2847:
2840:
2832:
2828:
2824:
2820:
2816:
2812:
2808:
2804:
2797:
2789:
2785:
2781:
2777:
2773:
2766:
2751:
2747:
2741:
2733:
2729:
2725:
2721:
2717:
2713:
2709:
2702:
2687:
2683:
2677:
2663:
2659:
2652:
2644:
2637:
2629:
2622:
2614:
2610:
2605:
2600:
2596:
2592:
2588:
2581:
2559:
2551:
2547:
2541:
2533:
2529:
2525:
2521:
2517:
2513:
2509:
2505:
2501:
2494:
2488:
2484:
2480:
2476:
2475:
2470:
2465:
2456:
2452:
2448:
2444:
2438:
2434:
2428:
2423:
2422:
2413:
2404:
2398:
2390:
2384:
2376:
2375:
2367:
2359:
2357:9780534389512
2353:
2349:
2348:
2340:
2333:
2329:
2325:
2321:
2318:Partialvalens
2317:
2311:
2307:
2303:
2300:(in German).
2299:
2295:
2288:
2280:
2276:
2269:
2263:
2255:
2251:
2244:
2238:
2230:
2226:
2222:
2218:
2214:
2210:
2209:J. Chem. Educ
2203:
2187:
2183:
2177:
2171:
2167:
2163:
2159:
2158:
2153:
2148:
2140:
2134:
2130:
2123:
2116:
2112:
2106:
2102:
2095:
2088:
2084:
2072:
2064:
2058:
2054:
2050:
2043:
2041:
2034:
2030:
2026:
2022:
2021:
2016:
2011:
2005:
2001:
1997:
1993:
1992:
1987:
1982:
1978:
1959:
1954:
1953:
1945:
1942:
1940:
1937:
1935:
1932:
1930:
1927:
1926:
1920:
1918:
1914:
1904:
1902:
1899:
1896:
1894:
1891:
1890:
1886:
1884:
1881:
1878:
1876:
1873:
1872:
1868:
1866:
1863:
1860:
1858:
1855:
1854:
1850:
1848:
1846:
1842:
1838:
1835:
1833:
1830:
1829:
1825:
1822:
1818:
1815:
1813:
1810:
1809:
1805:
1802:
1798:
1795:
1793:
1790:
1789:
1785:
1782:
1778:
1775:
1773:
1770:
1769:
1765:
1763:
1760:
1757:
1755:
1752:
1751:
1747:
1744:
1741:
1739:
1728:
1727:
1723:
1721:
1718:
1715:
1696:
1695:
1691:
1688:
1685:
1682:
1681:
1675:
1669:
1665:
1661:
1645:
1641:
1636:
1626:
1624:
1620:
1616:
1613:
1609:
1605:
1595:
1593:
1589:
1582:
1578:
1574:
1568:
1564:
1554:
1547:
1542:
1537:
1530:
1523:
1519:
1512:
1505:
1502: ≈
1501:
1493:
1488:
1481:
1477:
1473:
1469:
1464:
1461:
1456:
1451:
1444:
1439:
1434:
1430:
1426:
1417:
1408:
1405:
1402:
1401:variationally
1397:
1395:
1394:excited state
1390:
1389:wave function
1385:
1383:
1375:
1368:
1355:
1346:
1344:
1340:
1336:
1328:
1327:
1326:
1323:
1319:
1317:
1312:
1310:
1306:
1302:
1298:
1293:
1291:
1290:hydrogenation
1287:
1283:
1273:
1257:
1253:
1249:
1245:
1238:
1233:
1223:
1213:
1211:
1207:
1203:
1199:
1195:
1192:
1186:
1184:
1168:
1164:
1160:
1155:
1153:
1148:
1145:
1141:
1137:
1133:
1132:free radicals
1129:
1118:
1115:
1107:
1097:
1093:
1089:
1083:
1082:
1078:
1073:This section
1071:
1067:
1062:
1061:
1057:
1044:
1040:
1039:
1038:
1036:
1031:
1023:
1019:
1018:
1017:
1005:
999:
915:
914:
913:
911:
907:
903:
895:
891:
890:
889:
874:
860:
847:
843:
842:
841:
839:
835:
834:curved arrows
831:
827:
819:
815:
814:
813:
811:
807:
803:
799:
795:
791:
785:
770:
766:
764:
760:
756:
752:
748:
744:
739:
731:
728:
725:
722:
718:
715:
712:
708:
705:
701:
698:
695:
691:
687:
686:
685:
683:
679:
668:
666:
662:
658:
653:
651:
647:
643:
639:
635:
634:Hückel method
630:
628:
624:
623:zwischenstufe
620:
616:
612:
608:
604:
603:Linus Pauling
600:
596:
592:
588:
583:
580:
576:
571:
569:
565:
564:August Kekulé
561:
551:
548:
543:
541:
537:
526:
519:
510:
503:
490:
463:
455:
445:
432:
423:
415:
391:
389:
385:
381:
377:
373:
368:
366:
362:
358:
353:
351:
318:
307:
254:
250:
245:
241:
236:
232:
222:
220:
215:
212:
206:
204:
200:
199:formal charge
196:
191:
186:
180:
179:nitronium ion
172:
171:hydroxylamine
168:
164:
160:
143:
139:
137:
136:dipole moment
133:
129:
125:
121:
117:
113:
103:
101:
97:
93:
89:
85:
81:
77:
73:
69:
65:
61:
57:
53:
49:
45:
37:
32:
19:
3587:4674 Pauling
3506:
3479:
3471:
3468:(1949 paper)
3459:
3453:Publications
3308:
3246:6 (sextuple)
3213:multiplicity
3091:
3087:
3052:
3048:
3006:
3002:
2948:
2944:
2908:
2902:
2877:
2869:
2850:
2846:March, Jerry
2839:
2831:the original
2810:
2806:
2796:
2779:
2775:
2771:
2765:
2754:. Retrieved
2752:. 2020-06-21
2749:
2740:
2715:
2711:
2701:
2690:. Retrieved
2688:. 2015-04-01
2685:
2676:
2665:. Retrieved
2661:
2651:
2642:
2636:
2627:
2621:
2594:
2590:
2580:
2558:
2549:
2540:
2507:
2503:
2493:
2472:
2464:
2446:
2442:
2420:
2412:
2383:
2373:
2366:
2346:
2339:
2331:
2328:bezeichnet."
2327:
2323:
2319:
2315:
2301:
2297:
2287:
2274:
2262:
2249:
2237:
2212:
2208:
2202:
2190:. Retrieved
2185:
2176:
2155:
2147:
2128:
2122:
2114:
2100:
2094:
2071:
2052:
2018:
2010:
1989:
1981:
1962:. Retrieved
1910:
1844:
1840:
1792:Benzoic acid
1667:
1632:
1603:
1601:
1598:Coefficients
1584:
1583:C atoms and
1580:
1576:
1569:
1559:
1552:
1545:
1540:
1532:
1525:
1510:
1503:
1496:
1491:
1483:
1482:coefficient
1479:
1468:substituents
1465:
1459:
1454:
1446:
1445:coefficient
1442:
1437:
1422:
1398:
1396:, as shown.
1386:
1379:
1332:
1324:
1320:
1313:
1294:
1281:
1279:
1244:Bond lengths
1241:
1227:Bond lengths
1201:
1187:
1156:
1149:
1128:carbocations
1125:
1110:
1104:January 2017
1101:
1086:Please help
1074:
1027:
1004:allyl cation
1001:
899:
856:
823:
793:
787:
767:
763:dative bonds
735:
726:
720:
681:
677:
674:
654:
646:Erich Hückel
631:
626:
622:
611:C. K. Ingold
606:
584:
574:
572:
557:
544:
535:
533:
387:
383:
379:
375:
369:
354:
248:
243:
239:
228:
216:
210:
207:
203:multiplicity
194:
187:
166:
152:
128:bond lengths
109:
87:
83:
79:
75:
71:
67:
51:
47:
41:
3476:(1970 book)
3462:(1939 book)
3180:By symmetry
2377:, p. 1
1960:(in French)
1901:Propylamine
1832:Acetic acid
1754:Picric acid
1644:perchlorate
1635:carboxylate
1604:"Ab initio"
1305:cyclohexene
1297:cyclohexane
1198:carbocation
810:nodal plane
784:Aromaticity
743:hypervalent
730:biphenylene
724:Clar sextet
642:tautomerism
619:Fritz Arndt
58:in certain
3602:Categories
3390:Bonding MO
3374:MO diagram
3231:3 (triple)
3226:2 (double)
3221:1 (single)
2756:2024-02-07
2692:2024-02-07
2667:2024-02-07
2479:Mesomerism
2304:: 87–142.
2215:(2): 223.
1974:References
1964:29 October
1625:Web site.
1522:normalized
1309:exothermic
1256:bond order
1194:alkylation
873:bond order
751:sulfoxides
690:octet rule
607:mesomerism
240:depictions
163:bond order
120:octet rule
52:mesomerism
3507:Resonance
3335:Lone pair
3309:Resonance
3197:Delta (δ)
3187:Sigma (σ)
2813:(2): 28.
2732:0894-3230
2626:Wade, G.
2613:1365-3075
2532:145124799
2374:Resonance
2326:conjugirt
2192:7 October
1996:Resonance
1689:Compound
1683:Compound
1544:) ≈
1495:. Charge
1489:on atom C
1480:weighting
1460:occupying
1443:weighting
1404:optimized
1369:for the D
1339:thiophene
1167:methanium
1144:superacid
1075:does not
965:−
956:−
948:⟷
943:−
934:−
830:lone pair
599:frequency
464:≡
456:−
446:⊖
438:⟷
433:⊖
372:resonance
365:leviathan
326:⇀
319:−
308:−
301:↽
267:⟷
231:isomerism
82:) into a
60:molecules
48:resonance
44:chemistry
36:carbonate
3490:Concepts
3357:Concepts
3297:Concepts
3023:95538780
2973:20919704
2848:(2007),
2827:96029597
2548:(1954).
2397:cite web
1923:See also
1865:Pyridine
1615:Archived
1374:symmetry
1030:diborane
908:bond in
773:Examples
755:sulfones
702:carry a
547:pi bonds
106:Overview
3549:Related
3528:Founded
3270:Singlet
3265:Triplet
3202:Phi (φ)
2953:Bibcode
2524:4027009
2217:Bibcode
2087:benzene
1883:Aniline
1646:anion (
1335:pyrrole
1267:⁄
1237:benzene
1222:Benzene
1216:Benzene
1096:removed
1081:sources
1011:⁄
883:⁄
866:⁄
790:benzene
568:alkenes
554:History
525:benzene
509:nitrate
361:unicorn
357:narwhal
235:Isomers
159:nitrite
56:bonding
3558:(wife)
3482:(1986)
3192:Pi (π)
3142:theory
3021:
2971:
2915:
2890:
2886:–203.
2858:
2825:
2730:
2611:
2530:
2522:
2437:Hückel
2433:Slater
2354:
2135:
2107:
2059:
1812:Phenol
1779:MTBD (
1441:has a
1376:group.
1341:, and
1152:dienes
798:Kekulé
794:Kekulé
757:, and
442:
348:; see
195:formal
134:, and
132:angles
3019:S2CID
2823:S2CID
2528:S2CID
2520:JSTOR
2469:IUPAC
2279:IUPAC
2271:(PDF)
2254:IUPAC
2246:(PDF)
2152:IUPAC
2015:IUPAC
1986:IUPAC
1897:35.9
1879:29.1
1861:21.9
1836:16.1
1819:TBD (
1799:DBU (
1623:HuLiS
1577:ortho
1361:and B
1343:furan
1206:butyl
1035:3c-2e
906:3c-4e
859:ozone
826:furan
579:ortho
350:below
253:below
167:equal
90:) in
72:forms
3369:LCAO
3257:spin
2969:PMID
2913:ISBN
2888:ISBN
2856:ISBN
2728:ISSN
2609:ISSN
2435:and
2403:link
2352:ISBN
2194:2015
2133:ISBN
2105:ISBN
2057:ISBN
1966:2010
1905:8.9
1887:8.2
1869:7.2
1851:4.7
1826:3.5
1816:8.8
1806:3.0
1796:7.1
1786:2.9
1776:4.9
1766:2.6
1758:4.3
1748:2.5
1742:3.6
1724:2.1
1716:2.0
1612:NBO5
1581:para
1579:and
1474:and
1303:and
1299:via
1202:tert
1130:and
1079:any
1077:cite
1028:The
1002:The
900:For
857:The
575:four
86:(or
70:(or
3255:By
3211:By
3096:doi
3057:doi
3011:doi
2961:doi
2949:114
2884:200
2815:doi
2784:doi
2780:115
2772:cis
2720:doi
2599:doi
2570:Li)
2512:doi
2483:doi
2481:".
2451:doi
2427:184
2306:doi
2302:306
2225:doi
2166:doi
2164:".
2085:of
2029:doi
2027:".
2000:doi
1998:".
1893:HCl
1875:HBr
1738:COH
1730:(CF
1713:NH
1648:ClO
1423:In
1307:is
1288:of
1142:in
1140:NMR
1090:by
939:XeF
824:In
804:of
788:In
727:and
721:see
625:or
589:by
511:ion
244:not
173:, H
78:or
62:or
42:In
38:ion
3604::
3092:26
3090:.
3071:^
3053:87
3051:.
3047:.
3031:^
3017:.
3007:43
3005:.
2981:^
2967:.
2959:.
2947:.
2927:^
2821:.
2811:16
2809:.
2805:.
2778:.
2748:.
2726:.
2716:27
2714:.
2710:.
2684:.
2660:.
2607:.
2595:80
2593:.
2589:.
2526:.
2518:.
2508:25
2506:.
2502:.
2471:,
2447:53
2445:.
2399:}}
2395:{{
2277:,
2273:,
2252:,
2248:,
2223:.
2213:83
2211:.
2184:.
2154:,
2113:.
2051:.
2039:^
2017:,
1988:,
1857:HI
1823:)
1803:)
1783:)
1705:SO
1697:(C
1594:.
1538:AO
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