Fill in the blank by choosing the appropriate word/words from those given in the brackets.
(acetaldehyde, formaldehyde, benzaldehyde, yellow, white, violet, Cannizzaro's, Liebermann, no `alpha`-hydrogen atom, `1alpha`-hydrogen atom, `2alpha`-hydrogen atoms, aldol, `beta`-hydroxy aldehyde, aldol condensation, mixed condensation, + I,-I, -M,+ M. decreases, increases, benzalchloride, PCI, SOCh. sec, alcohol, tert, alcohol, phenylhydrozone, semicarbazone, more, less, acetals, ketals, silver mirror, test, urotropine, acetaldehyde cyanohydrin, lactic acid, benzoic acid, Sodalime, ethanoic acid, propanoic acid, electrolysis, Kolbe's electrolytic reaction, carbon dioxide, water, amides, alpha, halogen, phosphorus, weaker, stronger, ethyl alcohol, dibasic,monobasic, 2,2-dimethylpropanoic acid, `CH_(3)COCI`, acetic acid, `CH_(3)CH_(2)CH_(2)COOK`, enatiomers, diastereo, `K_(a)` `pk_(a)`, methanoic acid, higher, lower.)
Ethanol vapours are passed over heated copper and the product is treated with aqueous NaOH. The final product is........

Explanation

To solve the problem step by step, we will analyze the reaction of ethanol vapors with heated copper and the subsequent treatment with aqueous NaOH.

### Step 1: Identify the Initial Reaction
Ethanol (C2H5OH) is passed over heated copper. The heated copper acts as an oxidizing agent, which will oxidize ethanol to an aldehyde.

**Hint:** Remember that alcohols can be oxidized to aldehydes or ketones depending on the structure of the alcohol.

### Step 2: Determine the Product of Oxidation
...