What chemical tests could you do to distinguish between:?

Question

a. 2-bromoethanol and 1,2-dibromoethane
b. 2-hexanol and 1-hexene
c. 1-chloro-2-methyl-2-propanol and 1,2-dichloro-2-methylpropane
d. n-pentyne and 2-pentyne
e. butyl bromide and butane

Answer 1

For a,b,c add metal Na. The -OH group will readily react producing H2 gas.

For d use an aqueous solution of Ag+ and ammonia. You'll have a reaction only for n-pentyne giving a precipitate:
R-C-triple bond-C-H + Ag(NH3)2(+) -> R-C-trb-C-Ag (s) +NH3+ NH4(+)

For e, heat in a solution of NaOH (with ethanol-water as mixed solvent). Then acidify with HNO3 and finally add some AgNO3 solution. A very pale cream precipitate (AgBr) will form only for butyl-bromide. (Acidifying before adding AgNO3 is necessary to avoid Ag2O precipitation)

Answer 2

a. Alcohols can be derivatived by reacting with 3,5-dinitrobenzoyl chloride, forming an ester. This product is usually characterized by a melting point. 1,2-dibromoethane won't react with a benzoyl chloride.
b. Alkenes react with Br2, to form a vicinal dibromide. Consumption of bromine leads to a disappearance in red color. Alcohols do not react in this manner.
c. Use the same test as in a.
d. Measure the IR absorbance (around 2200 cm-1). The alkyne stretch in internal alkynes is very weak, whereas the stretch in terminal alkynes is observable.
e. Butyl bromide is a liquid at room temperature. Butane is a gas at room temperature. Good luck with this one.