Differentiate between the following :
(a) `(I)` Propanoic acid `(C_2 H_5 COOH)` and `(II)` acrylic acid `(CH_2 = CH - COOH)`.
(b) `(I) 2-`Bromo propanoic acid `(CH_3 CH Be COOH)` and `(II)` pyruvic acid `(MeCOCOOH)`
( c) `(I) 2-`Chloro-propanoic acid and `(II)` propanoic acid
(d) `(I)` Formic acid `(HCOOH)` and `(II)` acetic acid `(MeCOOH)`.
(e) `(I)` Malonic acid and `(II)` oxalic acid `((COOH)_2)`.
(f) `(I)` Malonic acid and `(II)` succinic acid
(g) `(I) n`-Butanolm (II) butanal, (III) dimethyl ether, `(IV)` butanoic acid, `(V)` butane.

Explanation

(a) `(II)` is also an alkene so it decolourises `Br_2//C Cl_4` solution, but `(I)` does not.
(b) `(II)` has a keto group , so it gives `2,4-DNP` test forming a red insoluble precipitate of `2,4-`dinitro phenyl hydrazone, but `(I)` does not.
( c) Both give precipitate with aqueous `AgNO_3`.
(II) `CH_3 CH_2 COOH + Ag^(oplus) rarr underset ("Soluble in" HNO_3) (CH_3 CH_2 COO^(Ө) Ag^(oplus)`.
(I)
But the precipitate with `(II)` dissolves on acidification with `HNO_3`, regenerating an acid.
But the white precipitate from `(I)` contains `AgCl`. which does not dissolve in aq. `HNO_3`.
(d) Due to the presence of aldehydic-type `H, (I)` is oxidised by acidic `KMnO_4` whose purple solution is decolourised. Moreover, `(I)` also gives positive Tollens and Fehling's solution test, but `(II)` does not give these tests.
( e) `(II)` does not give these tests.
( e) `(II)` on heating decomposes to `CO + H_2 O`
`(COOH)_2 overset (Delta) rarr CO_2 + H_2 O (I)` on heating gives `CO_2`.

(f) `(II)` on heating forms anhydride, but `(I)` does not.

(g) Add `NaHVO_3` , (IV) would evolve `CO_2`. Then add Tollens reagent, `[Ag(NH_3)_2]^(oplus) , (II)` would give `Ag` mirror.
Then add `Na` metal to the three remaining compounds, `(I)` would react with the evolution of `H_2` gas. Add `conc. H_2 SO_4` to the remaining two compounds, `(III)` would dissolve to give a warm solution. `(V)` is inert to all the above tests.