devongrrl - 23-7-2011 at 03:28
Would it be possible to use electrophilic aromatic substitution to add a Cl group ortho to benzyl alcohol producing 2-chloro benzyl alcohol ?
My thinking is that the alkyl chain which carries the OH would cause the Benzene to be activating and ortho-para directed ?
Also would the resultant molecule stop at being mono substituted or would the reaction go on to add a 2nd chlorine ?
Assuming the reaction did add one Cl group, I would end up with a mixture of both ortho and para and need to separatate the two ?
Bitburger - 23-7-2011 at 04:25
No, you definitely get a mixture of (2,4,6-trichlorophenyl)methanol, (2,4-dichlorophenyl)methanol, (4-chlorophenyl)methanol and
(2-chlorophenyl)methanol. The -CH2OH group INCREASE the reactivity of the benzene ring. -Cl slightly decrease the aromatic reactivity. Also, how will
you prevent the formation of benzyl chloride? Do you use aluminiumtrichloride for this reaction?
Actually I recommend to sulphonate first you benzyl alcohol and then performing your reaction to avoid the formation of
(2,4,6-trichlorophenyl)methanol and (2,4-dichlorophenyl)methanol. It seems impossible to prevent byproduct formation of the para chlorinated product
since I don't find a boiling point in my "Handbook of chemistry and physics 2010-2011" for the corresponding "benzene sulphonic acids".
I don't know whether or not it is useful to protect the alcohol group and if it is useful how to protect it without acid hydrolysis...
[Edited on 23-7-2011 by Bitburger]
smuv - 23-7-2011 at 20:06
Chlorinating an uprotected benzyl alcohol is tough, the "Cl+" necessary to chlorinate the ring is also sufficient to oxidize the alcohol.