22.26(a)An alkyl substituent on nitrogen is electron-releasing and base-strengthening; thus methyl-amine is a stronger base than ammonia. An aryl substituent is electron-withdrawing and base-weakening, and so aniline is a weaker base than ammonia.(b)An acetyl group is an electron-withdrawing and base-weakening substituent, especially whenbonded directly to nitrogen. Amides are weaker bases than amines, and thus acetanilide is aweaker base than aniline. Alkyl groups are electron-releasing; N-methylaniline is a slightlystronger base than aniline.(c)Chlorine substituents are slightly electron-withdrawing, and methyl groups are slightlyelectron-releasing. 2,4-Dimethylaniline is therefore a stronger base than 2,4-dichloroaniline.Nitro groups are strongly electron-withdrawing, their base-weakening effect being especiallypronounced when a nitro group is ortho or para to an amino group because the two groups arethen directly conjugated.(d)Nitro groups are more electron-withdrawing than chlorine, and the base-weakening effect of
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 10/03/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.