1. How many dideuterated biphenyls (Ph-Ph) exist?
I counted: 2-2', 2-3', 2-4' (2-5' and 2-6' are the same as 2-2' and 2-3' when the ring rotates around the Ph-Ph bond).
Then 3-3' and 3-4' (3-2' is the same as 2-3'). And only 4-4' left. All together, there are 3+2+1=6 biphenyls, but the answer is 12. Where am I wrong?
2. Just another quick one: Which of the following compounds can be reduced by NaBH4 to form an alcohol?
A) ketones B) aldehydes C) carboxylic acids D) esters E) ethers
Why only A and B? Couldn't it be C and D, too?