Question

Two gases $P$ and $Q$ both decolourise aqueous bromine but only one of them gives white ppt with Tollen’s reagent. $P$ and $Q$ are likely to be:

• A. $\text{HC}\equiv \text{CH}\text{and}{\text{CH}}_3–{\text{CH}}_2–C\equiv CH$
• B. $\text{HC}\equiv \text{CH}\text{and}{\text{CH}}_3–\text{C}\equiv \text{CH}$
• C. ${\text{CH}}_3–{\text{CH}}_2-\text{C}\equiv \text{CH}\text{and}{\text{CH}}_3–\text{C}\equiv \text{C}-{\text{CH}}_3$
• D. ${\text{H}}_2{\text{C=CH}}_2\text{and}{\text{CH}}_3–\text{C}\equiv \text{C}-{\text{CH}}_3$

Answer 1

The correct option is C ${\text{CH}}_3–{\text{CH}}_2-\text{C}\equiv \text{CH}\text{and}{\text{CH}}_3–\text{C}\equiv \text{C}-{\text{CH}}_3$

Only terminal alkyne gives white ppt. with tollen’s reagent. Alkene and alkyne both gives test of unsaturation with ${\text{Br}}_2/{\text{CCl}}_4$.