Halogenation of Carbon Aldehydes and Ketones - Handout | CHEM 343, Study notes of Organic Chemistry

Download Halogenation of Carbon Aldehydes and Ketones - Handout | CHEM 343 and more Study notes Organic Chemistry in PDF only on Docsity! 29 February Halogenation of the α-carbon of aldehydes and ketonescarbon of aldehydes and ketones If Br2, Cl2, or I2 is added to an acidic solution of an aldehyde or ketone, a halogen will replace one of the α-carbon of aldehydes and ketoneshydrogens of the carbonyl compound. If excess Br2, Cl2, or I2 is added to a basic solution rather than to an acidic solution of an aldehyde or a ketone, the halogen will replace all the α-carbon of aldehydes and ketoneshydrogens. The haloform reaction (in the presence of excess base and excess halogen, a metyl ketone will be converted into a carboxylic acid) CH3 – strong base, poor leaving group Halogenation of the α-carbon of aldehydes and ketonescarbon of carboxylic acids: the Hell-carbon of aldehydes and ketonesVolhard-carbon of aldehydes and ketonesZelinski reaction (HVZ reaction) Using Lithium Diisopropylamdie (LDA) to form an enolate LDA is a strong base but a poor nucleophile Removes H+ at α-carbon of aldehydes and ketonescarbon Kinetic vs thermodynamic product Kinetic product is the major product if the reaction is carried out at -carbon of aldehydes and ketones78° C. Thermodynamic product is the major product is the reaction is carried out under conditions that make enolate formation reversible (high temperature and a protic solvent so that the kinetic enolate can be reprotonated). Reaction of enamines An advantage of using an enamine intermediate to alkylate an aldehyde or ketone is that only the monoalkylated product is formed. When a carbonyl compound is alkylated directly, dialkylated and O-carbon of aldehydes and ketonesalkylated products can also be formed.