(i)

When benzaldehyde reacts with 2,4-dinitrophenylhydrazine then 2,4-dinitrophenylhydrazone is obtained as a product. 

The reaction is as follows:


(ii)
When cyclopropanone reacts with hydroxylamine then Cyclopropanone oxime is obtained as a product. 

The reaction is as follows:


(iii)

When acetaldehyde reacts with methanol in the presence of acid then acetaldehydedimethylacetal is obtained as a product.

The reaction is as follows:


(iv)
When cyclobutanone reacts with semicarbazide then semicarbazone is obtained as a product. The reaction is as follows:

(v)

When hexan-3-one reacts with ethylene glycol in the acidic medium then ethylene ketal is obtained as a product. The reaction is as follows:



(vi)
When formaldehyde reacts with 1 mole of CH₃OH then hemiacetal is obtained as a product. 

The reaction is as follows: