Methyl 4-oxopentanoate, CH3-CO-CH2CH2-COOCH3, is treated in sequence with (i) ethylene glycol, H+; (ii) LiAlH4, ether; (iii) H3O+ (aqueous work-up). The final product is

4-hydroxypentanoic acid methyl ester

JEE Main levelSingle correct optionDifficulty 2 of 3o1076

Methyl 4-oxopentanoate, $CH X_{3} - CO - CH X_{2} CH X_{2} - COOCH X_{3}$ , is treated in sequence with (i) ethylene glycol, $H X^{+}$ ; (ii) $LiAlH X_{4}$ , ether; (iii) $H X_{3} O X^{+}$ (aqueous work-up). The final product is

Step (i) protects the ketone as its ethylene ketal, which is inert to hydride.

LiAlH X_{4}

then reduces the ester to a primary alcohol. Aqueous acid removes the ketal and regenerates the ketone, giving

CH X_{3} - CO - CH X_{2} CH X_{2} CH X_{2} - OH