Advices For Studying Organic Chemistry

1) The solvent molecule has a hydrogen atom attached to an atom of a strongly

electronegative element.

2) In protic solvents, the nucleophile with larger nucleophilic atom is better.

i) Thiols (R–SH) are stronger nucleophiles than alcohols (R–OH); RS– ions are

more nucleophilic than RO– ions.

ii) The order of reactivity of halide ions: I– > Br– > Cl– > F–

3) Molecules of protic solvents form hydrogen bonds nucleophiles:

Molecules of the protic

solvent, water, solvate

a halide ion by forming

hydrogen bonds to it.

H

H X H

H

O

O

O

O H

H

H

H

−

i) A small nucleophile, such fluoride ion, because its charge is more concentrated,

is strongly solvated than a larger one.

4) Relative Nucleophilicity in Protic Solvents:

SH– > CN– > I– > HO– > N 3 – > Br– CH 3 CO 2 – > Cl–> F– > H 2 O

2. Polar Aprotic Solvent:
   
   
   1. Aprotic solvents are those solvents whose molecules do not have a hydrogen
      atom attached to an atom of a strongly electronegative element.
      i) Most aprotic solvents (benzene, the alkanes, etc.) are relatively nonpolar, and
      they do not dissolve most ionic compounds.
      ii) Polar aprotic solvents are especially useful in SN2 reactions:
   
   
   
   

C

O

HN

CH 3

CH 3 S

O

H 3 CCH (^3)
CH 3 C
O
N
CH 3
CH (^3)
P
O
(H 3 C) 2 NN(CH 3 ) 2
N(CH 3 ) (^2)
N,N-Dimethylformamide Dimethyl sulfoxide Dimethylacetamide Hexamethylphosphoramide