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Unformatted text preview: primary alcohol). CH 3 MgBr adds to acetaldehyde to give iso-propanol (a secondary alcohol), and CH 3 MgBr adds to acetone to give tert-butanol (a tertiary alcohol). CH 3 MgBr adds to carbon dioxide to give acetic acid. With the exception of phosphorus ylides, all carbon-nucleophiles we discuss will behave in an analogous fashion. The Wittig Reaction : Phosphorus ylides (e.g. Ph 3 P=CH 2 ) can be represented as a zwitterionic species in which the carbon bears a negative charge and the phosphorus bears a positive charge. Ylides will add to the carbonyl carbon of an aldehyde or ketone. The resulting alkoxide will bite back onto phosphorus to generate the famous oxaphosphetane intermediate: a 4-membered ring containing oxygen and phosphorus. This strained ring will collapse to give an alkene and triphenylphosphine oxide. The Wittig reaction can be thought of as the reverse of an ozonolysis....
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- Spring '08