can you tell me what is meant by alpha hydrogen of a ketone explain with example?

Answer 1

The alpha position is the position next to the functional group you are talking about. The alpha hydrogens of a ketone would be the hydrogens on the carbon next to the carbonyl.

Acetone CH3-C(O)_CH3

would have six alpha hydrogens.

Answer 2

An alpha hydrogen is on the carbon atom immediate adjoining the carboxyl carbon.
The hydrogen tends to be acidic since the ketone can resonate to form an "enol" or -CH=C(-OH)(-R)