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**课程汇总：醛、酮和羧酸** 本课程深入探讨了含有羰基 (>C=O) 的有机化合物，特别是醛和酮。这两种化合物具有相同的通式 CnH2nO。 **醛**的通用结构为 R-CHO，其中 R 可以是氢原子或烷基。最简单的醛是甲醛 (HCHO)，其羰基连接着两个氢原子。 **酮**的通用结构为 R-COR′，其中 R 和 R′ 可以是相同的或不同的烷基。 **羰基的结构与性质** * 羰基碳原子是 sp2 杂化，形成三个 sigma 键，一个与氧原子，另外两个与连接的原子或基团（R 或 H）。这三个 sigma 键位于同一平面，键角约为 120°。 * 羰基碳原子上未参与杂化的 p 轨道与氧原子上的未参与杂化的 p 轨道形成一个 pi 键。 * 由于碳和氧的电负性不同，C=O 键是极性键，氧原子带部分负电荷 (δ-)，碳原子带部分正电荷 (δ+)。 * 这使得羰基碳成为一个亲电中心，而羰基氧成为一个亲核中心。
Aldehydes and ketones are the compounds containing a carbonyl group, >C=O, in which a carbon atom is linked to an oxygen atom by a double bond. They have the same general formula CnH2nO.The general structure of aldehydes is R-CHO and that of ketones isR-COR′ where R and R′ may be same or different. Formaldehyde represents the simplest aldehyde in which the carbonyl group is attached to two hydrogen atom, i.e., R-CHO. Formaldehyde is exceptional in that the carbonyl group carries two hydrogen atoms and no alkyl substituents. It is, therefore, not surprising that it displays characteristic properties.Both aldehydes & ketones contain carbonyl group as their functional group.Structure of carbonyl groupBoth aldehydes & ketones have carbonyl group as the functional group. The carbonyl carbon is sp2 hybridized & it uses sp2 hybrid orbitals to form 3s bonds, one with oxygen atom & remaining 2 with two other atoms or groups (R or H). All these 3s bonds lie in same plane at the angle of 120°.The unhybridized p - orbital of carbonyl carbon form p- bond with oxygen atom by sidewise overlapping with phalf filled p - orbital of oxygen atom.Since carbon & oxygen have different values of electronegativity , the bond between carbon &oxygen is polar. Infact electron density around the oxygen atom is increased which causes the development of partial positive charge (d+) on carbon & partial negative charge (d-) on oxygen. Thus the carbonyl carbon is an electrophilic & carbonyl oxygen is nucleophilic centre.
