Question

What product will we get from the reaction (i) C6H5CHO + CH3CH2OH (reagent HCl)→ (ii) CH3CH2C(Cl)2CHO + H20 (reagent H+) → ?

Answer 1

The products are probably i) benzaldehyde ethyl hemiacetal and ii) 2,2-dichlorobutanal hydrate.

i). Benzaldehyde + ethanol

This reaction appears to be a the formation of a hemiacetal.

Alcohols undergo acid-catalyzed addition to aldehydes to form hemiacetals.

The reaction between benzaldehyde and ethanol is

`underbrace("C"_6"H"_5"CHO")_color(red)("benzaldehyde") + underbrace("HOCH"_2"CH"_3)_color(red)("ethanol") stackrelcolor(blue)("HCl"color(white)(m))→ underbrace("C"_6"H"_5"CH(OH)OCH"_2"CH"_3)_color(red)("benzaldehyde ethyl hemiacetal")`

ii) 2,2-Dichlorobutanal + water

Aldehydes undergo addition of water to form hydrates.

The reaction is catalyzed by acid and is greatly enhanced by electron withdrawing groups adjacent to the carbonyl group.

`underbrace("CH"_3"CH"_2"CCl"_2"CHO")_color(red)("2,2-dichlorobutanal") + "H"_2"O" stackrelcolor(blue)("H"^+color(white)(l)) → underbrace("CH"_3"CH"_2"CCl"_2"CH(OH)"_2)_color(red)("2,2-dichlorobutanal hydrate")`

The `"Cl"` atoms enhance the positive character of the carbonyl carbon and make it even more prone to nucleophilic attack by water.