Bonding in the carboxyllic acid group Watch
Do you know about resonance structures? If so, think about the resonance structures of the ethanoate ion (CH2COO-) compared to the phenoxide ion (C6H5O-). In each structure where are the electrons being dispersed to?
Think about the electronegativity of the atoms in each structure. Ethanoate contains another oxygen, whereas phenoxide contains only hydrogen and carbon, so the O- is the only oxygen in the molecule. How does this affect the electron densities in the dissociated structures? Where would they be attracted to, and how does this affect charges on the different areas of the molecule?
Molecules with less dispersion are less stable, as the negative charge is more concentrated around one point, so a H+ ion is more likely to just join back onto the molecule there as it is attracted by charge, whereas if there is a lot of dissociation, the H+ ions are not so strongly attracted to any particular part of the molecule, so it is less likely for them to join back on, and they will remain as H+ and A- for longer before joining back into HA.
In general, the carboxyl group consists of a carbonyl group (C=O) and a hydroxyl group (-OH). As the carbonyl group has a negative inductivity, the electrons of hydroxyl group are shifted to the C-atom of carbonyl group.
Crucial to the acidity is the inductivity of the alkyl rest. If the alkyl rest has a negative one, the attraction of electrons increases (the alkyl rest 'supports' the carbonyl group). If it is a positive one, the mentioned attraction decreases (the alkyl rest 'impedes' the carbonyl group).
Bonds of halogens (chlorine, fluorine...) have a negative inductive effect; hydroxyl groups, and methoxy groups (-OCH3) as well. Alkyl groups like methyl groups (-CH3) and ethyl groups (-C2H5) have a positive inductive effect instead. Just to name some well known examples.
Found out what functional groups or bonds the alkyl rest consists of. And I am sure you can solve 1a.) and 1b.)