[bavani]

may i know why the colour of dibenzalacetone is yellow? is it due to the uv spectrum or something? and why are equal quantities of acetone and benzaldehyde used.. i tried searching for the answers but have'nt been able to.. can someone help me!! i would really appreciate it. thanks

[priya22]

yes you are right about the color , Conjugation is responsible for the yellow color of dibenzalacetone.
 and regarding the EQUAL QUANTITIES of benzaldehyde and acetone.. I would like to remind you  that you need 2 MOLES of benzaldehyde and 1 MOLE of acetone to synthesize one MOLE of dibenzalacetone.
Hope this helps

[movies]

Then again, it's probably a lot easier to remove excess acetone from the reaction than to remove excess benzaldehyde.  It probably makes for nicer purification to use an excess of acetone.