價鍵異構體

價鍵異構體（Valence isomer），或稱作價異構體，是結構異構的一種，因分子中的價電子分佈發生了變化，並改變了分子的幾何形狀，故稱作價鍵異構。在有機化學中，特指能經週環反應進行互換的化合物。例如苯的化學式C6H6就不只有目前的模樣，杜瓦苯就是另一種擁有完全相同化學式，但其幾何形狀卻不同的化合物。除了杜克苯，在拓樸學的角度上，(CH)6這一家族還有極多可能的組合。但並非所有可能的組合都實際存在；這是因為環狀化合物的鍵長及鍵角的張力限制了其可能性。

**環丁二烯**
環丁二烯最簡單的n-輪烯（4-輪烯），它也有幾種異構體。
Image:Cyclobutadien.svg|環丁二烯
Image:Tetrahedrane.svg| 正四面體烷
Image:Bicyclo-1.1.0-but-1(3)-ene.png|Bicyclo-1.1.0-but-1(3)-ene

**苯**
Image:Benzene-2D-flat.png|苯，6個C-H鍵合連成環狀
Image:Dewar benzene (edge on).svg| 杜瓦苯，另一個結合6個C-H鍵而環狀的方法
Image:Prisman2.svg|稜柱烷，呈稜柱體的結構
Image:Benzvalene.png|盆苯，另一個苯的異構體
Image:Bicycloprop-2-enyl.svg|聯環丙烯，兩個環丙烯連結起來的化合物，這是其中較穩定的異構體

**環辛四烯**
除了(CH)6有為數不少的價鍵異構體，(CH)8家族同樣有價鍵異構體。而且與其他異構體的情況一樣，當分子體積增加，可能的異構體的數目亦會相對增加。
Image:Cyclooctatetraen.svg|環辛四烯    1,3,5,7-cyclooctatetraene
Image:Barrelene structure.png|桶烯    Bicyclo2.2.2octa-2,5,7-triene
Image:Cuban.svg|立方烷   Pentacyclo4.2.0.02,5.03,8.04,7octane
Image:Cuneaan.png|楔形烷   Pentacyclo3.3.0.0 2,4.03,7.06,8octane
Image:Semibullvalene.svg|半瞬烯 (4as,4bs)-2a,2b,4a,4b-Tetrahydrocyclopropacdpentalene
Image:1,5-dihydropentalene.png|1,5-dihydropentalene
Image:2a,2b,4a,4b-tetrahydrocyclopropa cd pentalene.png|2a,2b,4a,4b-Tetrahydrocyclopropacdpentalene
Image:Bicyclo420octa247triene.svg|Bicyclo4.2.0octa-2,4,7-triene.
Image:Tricyclo33006octa38diene.svg|Tricyclo3,3,0,02,6octa-3,8-diene.
Image:Cyclobutadiene dimer cis trans.svg|Tricyclo4,2,0,02,5octa-3,7-diene.
Image:Tetracyclooctaene.svg|Tetracyclo3,3,0,02,4,03,6 octa-7-ene.
Image:Tetracyclooct-7-ene.svg|Tetracyclo4,2,0,02,4,03,5 octa-7-ene.
Image:Octabisvalene.svg| Pentacyclo5.1.0.02,4. 03,5.06,8octane (octabisvalene).
Image:Octavalene.svg| Tricyclo5.1.0.02,8octa-3,5-diene (octavalene).

**10輪烯**
10輪烯的價鍵異構體
Image:10-annulene-5.png|center|600px|10annulenes

**萘**
Image:Naphthalene-2D-Skeletal.svg|萘
Image:Azulene-numbers.png| 薁
Image:2a,4a,6a,6b-tetrahydrocyclopenta cd pentalene.png|2a,4a,6a,6b-tetrahydrocyclopentacdpentalene
Image:4,4a,6a,6b-tetrahydro-Cyclopenta cd pentalene.png|Isotriquinacene   4,4a,6a,6b-tetrahydro-Cyclopentacdpentalene
Image:1,3-dicyclopentylcyclopentane.png|1,3-dicyclopentylcyclopentane
Image:1-Cyclodecene-3,9-diyne.png|1-Cyclodecene-3,9-diyne
Image:1,1'-Bi(cyclopentane)-1,2',3,4'-tetraene.png|1,1'-Bi(cyclopentane)-1,2',3,4'-tetraene
Image:1-Phenyl-bicyclo 1.1.0 butane.png|1-phenyl-bicyclo1.1.0butane
Image:3-phenylcyclobutene.png|3-phenylcyclobutene
Image:(5E,7Z)-1,3,5,7,9-Cyclodecapentaene.png|(5E,7Z)-1,3,5,7,9-Cyclodecapentaene
Image:(1β,2α,3β,6β,7α,8β)-Tetracyclo 6.2.0.02,7.03,6 deca-4,9-diene.png|(1β,2α,3β,6β,7α,8β)-Tetracyclo6.2.0.02,7.03,6deca-4,9-diene
Image:1,3,4,5-Tetrahydrocycloprop f indene.png|1,3,4,5-Tetrahydrocyclopropfindene
Image:1,1a,6,6a-tetrahydro-Cycloprop a indene.png|1,1a,6,6a-tetrahydro-Cyclopropaindene
Image:1,4-Cyclo-1,4,4a,8a-tetrahydronaphthalene.png|1,4-Cyclo-1,4,4a,8a-tetrahydronaphthalene
Image:Tricyclo 6.2.0.03,6 deca-1,3(6),7-triene.png|Tricyclo6.2.0.03,6deca-1,3(6),7-triene
Image:Tricyclo(6.2.0.0 2,5)deca-1,5,7-triene.png|2,5-dimethoxythiophene
Image:Tricyclo 5.3.0.02,8 deca-3,5-diene.png|Tricyclo5.3.0.02,8deca-3,5-diene
Image:4,7-dihydro-4,7-Methano-2H-indene.png|4,7-dihydro-4,7-Methano-2H-indene
Image:3a,4,5,7a-tetrahydro-1,4,5-Metheno-1H-indene.png|3a,4,5,7a-tetrahydro-1,4,5-Metheno-1H-indene
Image:1,2,3-Metheno-1H-cycloprop cd indene,2,2a,2b,3,5a,5b-hexahydro- (8CI,9CI).png|Snoutene   2,2a,2b,3,5a,5b-hexahydro-1,2,3-metheno-1H-cyclopropcdindene
Image:1,3a,4,6a-tetrahydro-1,4-Ethenopentalene.png|Lumibullvalene   1,3a,4,6a-tetrahydro-1,4-Ethenopentalene
Image:Bicyclo 4.2.2 deca-2,4,7,9-tetrene.png|Bicyclo4.2.2deca-2,4,7,9-tetrene
Image:2a,2b-Ethano-4a,4b-dihydrocyclopropa cd pentalene.png|2a,2b-Ethano-4a,4b-dihydrocyclopropacdpentalene
Image:Tetracyclo 5.3.0.02,6.03,10 deca-4,8-diene.png|Hypostrophene   Tetracyclo5.3.0.02,6.03,10deca-4,8-diene
Image:Octahydro-3-methylene-1,2-Methanodicyclopropa(cd,gh)pentalene.png|Octahydro-3-methylene-1,2-Methanodicyclopropa(cd,gh)pentalene
Image:Basketeen.png|Basketene   Pentacyclo4.4.0.02,5.03,8.04,7dec-9-ene
Image:Pentacyclo 5.3.0.02,5.03,9.04,8 decane-2-ene.png|Pentacyclo5.3.0.02,5.03,9.04,8decane-2-ene
Image:Hexacyclo 4.4.0.02,5.03,9.04,8.07,10 decane.png|Pentaprismane   Hexacyclo4.4.0.02,5.03,9.04,8.07,10decane
Image:3,6,9-Methylidynetetracyclo_6.1.0.02,4.05,7_nonane.png|Diademane     Octahydro-1,2,3-metheno-1H-dicyclopropcd,hiindene
Image:Bullvalene.svg|瞬烯      Tricyclo3.3.2.02,8deca-3,6,9-triene
Image:2,3-dihydro-1,3-methano-1h-indene.png|2,3-dihydro-1,3-methano-1h-indene
Image:Bicyclo 4.3.1 deca-2,4,6,8-tetraene.png|Bicyclo4.3.1deca-2,4,6,8-tetraene
Image:4,7-Methano-4,7-dihydro-1H-indene.png|4,7-Methano-4,7-dihydro-1H-indene
Image:Tricyclo 4.2.2.02,5 deca-3,7,9-triene1.png|Tricyclo4.2.2.02,5deca-3,7,9-triene
Image:Bicyclo 4.2.2 deca-2,4,7,9-tetraene.png|Bicyclo4.2.2deca-2,4,7,9-tetraene
Image:Hexacyclo 6.2.0.01,9.02,4.03,5.07,9 decane.png|Hexacyclo6.2.0.01,9.02,4.03,5.07,9decane
Image:2a,2b,6a,6b-Tetrahydrocyclopropa cd azulene-1.png|2a,2b,6a,6b-Tetrahydrocyclopropacdazulene
Image:(2S,3S,6S,7S)-Pentacyclo 4.4.0.02,5.03,8.04,7 dec-9-ene.png|(2S,3S,6S,7S)-Pentacyclo4.4.0.02,5.03,8.04,7dec-9-ene
Image:(1R,5R,6S,7S,8R,10S)-Hexacyclo 6.2.0.02,4.02,10.03,6.05,7 decane.png|(1R,5R,6S,7S,8R,10S)-Hexacyclo6.2.0.02,4.02,10.03,6.05,7decane
Image:C10H10.png

**參考文獻==