Write the structures of the main products of the following reactions:
(a) CH$_3$CH$_2$-C$\equiv$O + NaBH$_4$
(b) 6CH$_3$C$\equiv$O + 2AlCl$_3$ $\rightarrow$ 6CH$_3$C$\equiv$O
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When using NaBH$_4$, remember it reduces aldehydes and ketones to alcohols. Friedel-Crafts acylation typically involves the addition of an acyl group to an aromatic ring.
(a) The reaction of an aldehyde with NaBH$_4$ (sodium borohydride) reduces the carbonyl group to an alcohol. The product is CH$_3$CH$_2$-CH$_2$OH (ethanol).
(b) In the second reaction, the presence of AlCl$_3$ induces a Friedel-Crafts acylation reaction, resulting in the formation of 6 molecules of CH$_3$C$\equiv$O (acetyl) groups attached to aromatic rings. The main product is 6 molecules of acetophenone (C$_6$H$_5$COCH$_3$).
