The reaction of a saturated monoalcohol $A$ on an unsaturated carboxylic acid $B$ forms an ester $E$.
$3.7\;g$ of $B$ was obtained by hydrating $2.8\;g$ of an alkene $F$.
Deduce the molecular formula of $B$ and possible condensed formulas.
The controlled oxidation of $B$ gives a compound which reacts with DNPH but not with Fehling's solution.
What is the condensed formula of $B$?
$V=50\;cm^3$ aqueous solution containing $0.400\;g$ of $A$ consumes $17.5\;mL\;0.5\;M \;NaOH$ by titration.
Find the condensed formula of $A$
Find the condensed formula of $E$ and its name.
1)
Hydratation reaction:
$C_nH_{2n}$ $+$ $H_2O$ $\rightarrow$ $C_nH_{2n+2}O$
Alcene + water $\rightarrow$ alcohol
x mol alcene give x mol alcohol:
$\frac{x\cdot M_{F}}{x\cdot M_{B}}$ $=$ $\frac{14n}{14n+18}$ $=$ $\frac{2.8}{3.7}$
so $n$ $=$ $4$
Molecular formula of $ B$:
$C_4H_{10}O$
$B$ is a secondary alcohol:
Condensed formula of $B$:
$CH_3CHOHCH_2CH_3$
2)
Titration:
At equivalence:
$n_{acid}$ $=$ $n_{NaOH}$ $=$ $0.5\cdot 0.0175$ $=$ $0.00875$
$M_{acid}$ $=$ $\frac{0.400}{0.00875}$ $\approx$ $46 \frac{g}{mol}$
General formula:
$C_nH_{2n}O_2$
$12n$ $+$ $2n$ $+$ $32$ $=$ $46$
$n$ $=$ $1$
Molecular formula:
$CH_2O_2$
Condensed formula of $A$:
$HCOOH$
$E$ is 1-methylpropylmethanoate
$HCOOCH(CH_3)CH_2CH_3$
