Question

Rank the following active methylene compounds in order of decreasing acid strength.

Answer 1

A group CH2 - that present adjacent to carbonyl group or other groups present in a molecule iscalled as active methylene group and these type of molecules are known as active methelenes.The hydrogens present in that group are more acidic in nature. The acidic strength of the methylene group depends on the nature of the adjacent group. The - NO2 group is strong electron withdrawing group than carbonyl and cyanide groups, thus, the compound that contains two nitro groups is more acidic than all other compounds. Carbonyl group is strong withdrawing group than cyanide group. Ester group is weakest electron with drawing group, hence the dimethyl malonate would be least acidic.

Thus, order of acidic strength of the molecules is as follows NO2 NO2 CN > dinitromethane 1-nitropropan-2-one pentane-2,4-dione 3-oxobutanenitrile MeO OMe dimethyl malonate

Answer 2

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Answer 3