This is taken from Organic Chemistry 8th Edition of T. W. Graham Solomons and Craig B. Fryhle. This is just what I've understood so far. So, correct me if I'm wrong.
Basically, the following points leads to increased acidity of molecules.
- Charge delocalization, e.g. CH3NH2 is more acid than CH4.
- Greater s orbital character in carbon hybridization, e.g. CH3CH=CH2 is more acid than CH3CH2CH3.
- Lower position within a group of the periodic table, e.g. HCl is more acid than HF.
- Position further to the right within a given row of the periodic table, e.g. HCl is more acid than H2S.
But I do have problems. For example, problem 3.28.B.
Interestingly, I did that rightly. I thought that CH3CHClCO2H is the most acid because the chlorine atom and the two oxygen atoms provide more charge delocalization than the two oxygen atoms do in CH2CH2CO2H. Based on the same reason, CH2CH2CO2H is more acid than CH3CH2CH2OH.Arrange the following compounds in order of decreasing acidity.
CH3CH2CH2OH
CH3CH2CO2H
CH3CHClCO2H
But how about the following groups?
- CH3CH2OH2+, CH3CH2OH and CH3OCH3.
- CH3NH3+, CH3NH2 and CH3NH-.
I'm thinking that how stabile the anion of a compound, how more acid the compound is. But I don't have any courage to use it as an assumption.
Any help would be appreciated greatly.
p.s. How can you do subscripts with BBCode?