Distinguishing Test for Organic Compounds

Given the following pairs of samples, how do I distinguish between them?

1. benzamide vs ethanamide
2. ethanoyl chloride vs ethanoic anhydride

My Approach:

1. We could easily convert the amides to amines by reducing them with $\ce{LiAlH4}$. Now, the question reduces to identifying the methyl group against the benzene group.

2. I am really lost here but my guess would be that we are looking for some characteristic reaction for Anhydrides.

• This seems like a homework question. We ‎have a policy which states that you should show your thoughts and/or efforts into solving the ‎problem. It'll make us certain that we aren't doing your homework for you. Otherwise, this ‎question may get closed. – bon Oct 26 '15 at 14:46
• @bon I have updated the question to show my efforts but otherwise, I'm reallly lost here. – Agnishom Chattopadhyay Oct 26 '15 at 15:01
• Well what reactions do benzene rings undergo that methyl groups don't? – bon Oct 26 '15 at 15:04
• Flame Test: Sooty Flame appears when Aromatic Compounds are put on the bunsen flame – Agnishom Chattopadhyay Oct 26 '15 at 17:20
• This is hardly a very accurate test. Can you think of any other reactions that might work. – bon Oct 26 '15 at 17:32

1. Benzamide would have peaks characterizing an aromatic ring, for example: $\ce{C}_{sp^2}\ce{-H}$ stretches around $3050-3100\ \mathrm{cm^{-1}}$. Ethanamide will not have these peaks, but will instead have $\ce{C}_{sp^3}\ce{-H}$ peaks $2800-3000\ \mathrm{cm^{-1}}$. There are other differences as well.