A mixture of an acid anhydride (A) anda mono basic acid (B) on heating produces another mono basic acid (C) of equivalent weight 74 and m an anhydride (D). The acids and anhydrides remain in equilibrium. The anhydride (D) contains two identical fluoro alkyl groups. The acid (B) contains a trifluoro methyl group and has an equivalent weight of 128. Give structures of (A) to (D) with proper reasoning (Atomic weight of fluorine =19).

A mixture of an acid anhydride (A) anda mono basic acid (B) on heating

1.	A mixture of an acid anhydride (A) anda mono basic acid (B) on heating produces another mono basic acid (C) of equivalent weight 74 and m an anhydride (D). The acids and anhydrides remain in equilibrium. The anhydride (D) contains two identical fluoro alkyl groups. The acid (B) contains a trifluoro methyl group and has an equivalent weight of 128. Give structures of (A) to (D) with proper reasoning (Atomic weight of fluorine =19).
Answer» Solution :`underset((A))((RCO)_2)O+2R'-underset((B))(COOH)tounderset("MOL.wt.74")underset((C))(2RCOOH)+underset((D))(R'CO)_2O` Mol. Wt. of `R-COOH=74,R+12+32+1=74,R=74-45=29(C_2H_5)` Thus, (C) is `CH_3CH_2COOH` and on the basis of above reaction, acid anhydride (A) is `(C_2H_5CO)_2O`.The acid anhydride (D) contains two identical fluoro alkyl groups. The acid (B) contians a trifluoro methyl group and has an equivalent weight of 128. Hence, mono basic acid (B) is `CF_3CH_2COOH` and so, acid anhydride (D) is `(CF_3CH_2CO)_2O`. Reactions: `underset((A))((CH_3CH_2CO)_2O)+underset("Eq.wt.=128")underset((B))(CF_3CH_2COOH)tounderset("Eq.wt.= 74")underset((C))(CH_3CH_2COOH)+underset((D))((CF_3CH_2CO)_2O)`.