trans-Stilbene, C6H5-CH=CH-C6H5, is treated with cold, dilute KMnO4 to give a diol, which is cleaved completely by HIO4. The organic product is then treated with excess Tollens' reagent. How many moles of silver are deposited per mole of stilbene (aldehyde -> acid, Ag+ to Ag)?

JEE Advanced levelSingle correct optionDifficulty 3 of 3ro089

trans-Stilbene, $C X_{6} H X_{5} - CH = CH - C X_{6} H X_{5}$ , is treated with cold, dilute $KMnO X_{4}$ to give a diol, which is cleaved completely by $HIO X_{4}$ . The organic product is then treated with excess Tollens' reagent. How many moles of silver are deposited per mole of stilbene (aldehyde $\to$ acid, $Ag X^{+}$ to $Ag$ )?

Syn dihydroxylation gives 1,2-diphenylethane-1,2-diol, and

HIO X_{4}

cleaves it into 2 mol of benzaldehyde. Each aldehyde group reduces 2

Ag X^{+}

to 2 Ag in Tollens' reagent (

RCHO

RCOO X^{-}

is a 2-electron oxidation). Silver deposited

= 2 \times 2 = 4

mol.