Oxidation of alcohols by strong oxidants in acid medium

Exercise 7

A controlled oxidation of an alcohol $A$ with 4 carbon atoms is carried out with a potassium dichromate solution in acidic medium. This gives a ketone. 1) Give the empirical formula of $A$, its semi-structural formula and name. 2) Write a detailed redox sytem 3) In the same way is treated a primary alcohol $B$, isomer of $A$. $B$ has a branched chain. Write the detailed redox systems!

1) $A$: $C_4H_{10}O\;CH_3CHOHCH_2CH_3$ butan-2-ol 2) $CH_3CH_2CHOHCH_3$ $-$ $2e^-$ $\rightarrow$ $CH_3CH_2COCH_3$ $+$ $2H^+$ $Cr_2O_7^{2-}$ $+$ $6e^-$ $+$ $14H^+$ $\rightarrow$ $2Cr^{3+}$ $+$ $7H_2O$ $3CH_3CH_2CHOHCH_3$ $+$ $Cr_2O_7^{2-}$ $+$ $8H^+$ $\rightarrow$ $3CH_3CH_2COCH_3$ $+$ $2Cr^{3+}$ $+$ $7H_2O$ 3) $B$: $CH_3CH(CH_3)CH_2OH$ 2-méthylpropan-1-ol 1st step: $CH_3CH(CH_3)CH_2OH$ $-$ $2e^-$ $\rightarrow$ $CH_3CH(CH_3)CHO$ $+$ $2H^+$ $Cr_2O_7^{2-}$ $+$ $6e^-$ $+$ $14H^+$ $\rightarrow$ $ 2Cr^{3+}$ $+$ $7H_2O$ $3CH_3CH(CH_3)CH_2OH$ $+$ $Cr_2O_7^{2-}$ $+$ $8H^+$ $\rightarrow$ $3CH_3CH(CH_3)CHO$ $+$ $2Cr^{3+}$ $+$ $7H_2O$ Product: 2-methylpropanal 2nd step: $CH_3CH(CH_3)CHO$ $-$ $2e^-$ $+$ $H_2O$ $\rightarrow$ $CH_3CH(CH_3)COOH$ $+$ $2H^+$ $Cr_2O_7^{2-}$ $+$ $6e^-$ $+$ $14H^+$ $\rightarrow $ $2Cr^{3+}$ $+$ $7H_2O$ $3CH_3CH(CH_3)CHO+Cr_2O_7^{2-} +8H^+\rightarrow$$3CH_3CH(CH_3)COOH + 2Cr^{3+}+4H_2O$ Product: 2-methylpropanoic acid