.. The Addition of Hydrogen Cyanide • Aldehydes and ketone react with HCN to form a cyanohydrin – A catalytic amount of cyanide helps to speed the reaction

Cyanohydrin

١ Dr. Abdullah Saleh // Defense system of millipede & bombardier beetle (apheloria corrugata )

N H O OH enzyme catalyst + HCN

Benzaldehyde Cyanohydrin

٢ Dr. Abdullah Saleh // Problem .

// Dr. Abdullah Saleh Recap

// Dr. Abdullah Saleh . Addition of Nitrogen Nucleophiles

// Dr. Abdullah Saleh • The Addition of Primary and Secondary Amines • Aldehydes and ketones react with primary amines (and ammonia) to yield imines – They react with secondary amines to yield enamines

٦ Dr. Abdullah Saleh // ٧ Dr. Abdullah Saleh // Examples

// Dr. Abdullah Saleh // Dr. Abdullah Saleh // Dr. Abdullah Saleh . Reduction of Carbonyl Compounds

// Dr. Abdullah Saleh Examples

// Dr. Abdullah Saleh Reducing C=O without C=C

. O OH

CCH3 CHCH3 NaBH?

Not readily attacked by nucleophiles,nucleophiles , metal hydrides

// Dr. Abdullah Saleh // Dr. Abdullah Saleh . Oxidation of Carbonyl Compounds

// Dr. Abdullah Saleh Other Oxidizing Agents

// Dr. Abdullah Saleh Tollens’ Test (Silver Mirror Test)

• Aldehydes and ketones can be distinguished from each other on the basis of the Tollens test – The presence of an aldehyde results in formation of a silver mirror (by oxidation of the aldehyde and reduction of the silver cation) – α-Hydroxyketones also give a positive Tollens’ test

// Dr. Abdullah Saleh Examples

Which of the following compounds will give a positive silver mirror test (Tollens’ test)?

O e. H3C C OCH3 a. c. CH2OCH3 CH(OCH3)2

. O

*d. H C CH O . b. 3 . H3C C CH3

// Dr. Abdullah Saleh . Keto-Enol Tautomerism

Hydrogens on carbons α to carbonyls are unusually acidic The resulting anion is stabilized by resonance to the carbonyl

// Dr. Abdullah Saleh . Acidity of α-Hydrogens; the Enolate Anion

// Dr. Abdullah Saleh // Dr. Abdullah Saleh – The enolate anion can be protonated at the carbon or the oxygen • The resultant enol and keto forms of the carbonyl are formed reversibly and are interconvertible

Chapter • Enol-keto tautomers are constitutional isomers that are easily interconverted by a trace of acid or base –Most aldehydes and ketones exist primarily in the keto form because of the greater strength of the carbon -oxygen double bond relative to the carbon-carbon double bond

// Dr. Abdullah Saleh • Keto and Enol Tautomers

Chapter Resonance contributors to the enolate anion of cyclohexanone & acetaldehyde

٢٥ Dr. Abdullah Saleh // End of Chapter Dr. Abdullah I. Saleh

// Dr. Abdullah Saleh