A chloro compound (A) showed the following properties : (i) decolourised bromine in C CI_4, (ii) absorbed hydrogen catalytically , (iii) gave a precipitate with ammoniacal Cu_2CI_2, (iv) when vapourised 1.49g of (A) gave 448mL of vapour at STP. Identify (A) and write down the equation of reaction at step (iii).

A chloro compound (A) showed the following properties : (i) decolouri

1.	A chloro compound (A) showed the following properties : (i) decolourised bromine in C CI_4, (ii) absorbed hydrogen catalytically , (iii) gave a precipitate with ammoniacal Cu_2CI_2, (iv) when vapourised 1.49g of (A) gave 448mL of vapour at STP. Identify (A) and write down the equation of reaction at step (iii).
Answer» Solution :The (i) and (ii) properties show that the chloro compound (A) is an unsaturated compound having double or triple bond. The compound GIVES a precipitate with ammoniacal `Cu_2ci_2`. It is , therefore, an ALKYNE having acidic hydrogen ,i.e., `-C-=CH`. Determination of molecular mass: 448mL of the compound WEIGHTS at `STP=1.49 g` `22400mL` of the compound will weigh at STP `=(1.49)/(448)xx22400` Mol. mass `=74.5` Let the formula of the compound be `RCI=-C-=CH` The formula mass `=R+CI+(-C-=CH)=74.5` `R+35.5+25=74.5` `R+60.5=74.5` So, `R=14` i.e., `CH_2` The STRUCTURE of compound (A) is `overset(CI)overset(\|)CH_2-C-=CH`. EQUATION of step (iii). `overset(CI)overset(\|)(2CH)_2-C-=CH+Cu_2CI_2overset(NH_4OH)tooverset(CI)overset(\|)(2CH)_2-C-=C-Cu+2HCI`