**注意**：本页有UnihanB区汉字：「𨦡」，這些可能會错误显示，詳见Unicode汉字。

**碳－氧键**是指碳原子和氧原子之间形成的共价键，这是有机化学和生物化学中最常见的化学键之一。氧原子具有6个价电子，倾向于与碳原子共用两个电子形成化学键，剩下的四个非键电子形成两对孤对电子。最简单的含碳－氧键化合物是醇，它们可以看作水的有机衍生物。

碳－氧键是强极性键，电子云明显偏向氧（电负性：碳2.55，氧3.44）。石蜡族的碳–氧键键长平均在143皮米左右，比碳－氮键或碳－碳键都要短。羧酸中单键键长更短（136pm），其中因为共轭效应的存在而具有部分双键的性质。环氧化合物中键长更长（147pm），因为角张力的存在使得电子云不能很好地重叠。碳–氧键的键能也比碳－氮键或碳–碳键大。例如，298K时，甲醇中C-O键键能为91 kcal/mol，甲胺中C-N键键能为87 kcal/mol，而乙烷中C-C键键能为87 kcal/mol。

含有端基碳氧双键官能团的化合物统称为羰基化合物，包括醛、酮、羧酸、羧酸衍生物等等。分子内部的碳氧双键存在于带正电的𨦡盐离子中，但它们多以反应中间体的形式存在。在呋喃及其衍生物中，氧原子的孤对电子参与了p-π共轭，因此呋喃是芳香性的。羰基化合物中碳氧双键的键长约为123 pm。而酰卤中的碳氧双键具有部分三键的性质，因此键长只有 117 pm。常見的碳氧三键只在一氧化碳分子中存在，其中键长很短（112.8 pm）、键能很大。这样的三键键能很大，甚至比氮氮三键的键能还高。氧也可以形成三价的化合物，例如氟硼酸三甲基𨦡。

化学
--

生成碳－氧键的重要反应有Williamson醚合成、亲核酰基取代反应和烯烃的亲电加成反应。Paternò–Büchi反应相当于羰基进行的复分解反应。

含氧官能团
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碳–氧键存在于以下这些官能团中：

| 化学分类 | 键级 | 化学式 | 结构式 | 例子 |
| --- | --- | --- | --- | --- |
| 醇 | 1 | R3C–OH | Alcohol | Ethanol乙醇 |
|
| 醚 | 1 | R3C–O–CR3 | Ether | Diethyl ether乙醚 |
| 过氧化物 | 1 | R3C–O–O–CR3 | Hydroperoxide | Di-tert-butyl peroxide二叔丁基过氧化物 |
|
| 酯 | 1 和 2 | R3C–CO–O–CR3 | Ester | Ethyl acrylate丙烯酸乙酯 |
|
| 碳酸酯 | 1 | R3C–O–CO–O–CR3 | Carbonate ester | Ethylene carbonate碳酸乙二酯 |
|
| 酮 | 2 | R3C–CO–CR3 | Ketone | Acetone丙酮 |
|
| 醛 | 2 | R3C–CHO | Aldehyde | Acrolein丙烯醛 |
|
| 羧酸 | 1 和 2 | R3C–COOH | 羧酸 | 乙酸乙酸 |
|
| 呋喃 | 1.5 |  | Furan | Furfural糠醛 |
|
| 吡喃鎓盐 | 1.5 |  | pyridine | Anthocyanin花色苷 |
|

参见
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* 元素周期表中其他元素与碳形成的化学键：

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 

| * 
* 论
* 编
元素周期表中与碳成键所形成的化合物 |
| --- |
|  |
| 

|  |  |  |  |  |
| --- | --- | --- | --- | --- |
| CH |  |  |  | He |
| CLi | CBe | CB | CC | CN | CO | CF | Ne |
| CNa | CMg | CAl | CSi | CP | CS | CCl | CAr |
| CK | CCa |  | CSc | CTi | CV | CCr | CMn | CFe | CCo | CNi | CCu | CZn | CGa | CGe | CAs | CSe | CBr | CKr |
| CRb | CSr |  | CY | CZr | CNb | CMo | CTc | CRu | CRh | CPd | CAg | CCd | CIn | CSn | CSb | CTe | CI | CXe |
| CCs | CBa | 1 asterisk | CLu | CHf | CTa | CW | CRe | COs | CIr | CPt | CAu | CHg | CTl | CPb | CBi | CPo | CAt | Rn |
| Fr | CRa | 2 asterisks | Lr | Rf | Db | CSg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
|   |
|  | 1 asterisk | CLa | CCe | CPr | CNd | CPm | CSm | CEu | CGd | CTb | CDy | CHo | CEr | CTm | CYb |
|  | 2 asterisks | Ac | CTh | CPa | CU | CNp | CPu | CAm | CCm | CBk | CCf | CEs | Fm | Md | No |

 |
|  |
| 图例 | * 与碳所成的化学键系
* 有机化学重要研究对象
* 有广泛应用的领域
* 仅是学术研究的对象
* 尚未发现此类键
 |

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参考资料
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1. ↑  *Organic Chemistry* John McMurry 2nd Ed.
2. ↑  CRC Handbook of Chemistry and Physics 65Th Ed.
3. ↑  Standard Bond Energies 的存檔，存档日期2016-08-29. Department of Chemistry, Michigan State University