[juaner]

Hello, i am trying to chlorinate the hydroxyl groups of the mandelic acid. I have tried with thionyl chloride but i have not been successful, can someone give an idea about how to do it, or what other reactive can i use to chlorinate these groups.

Thank you. 

[Dan]

Hello, i am trying to chlorinate the hydroxyl groups of the mandelic acid.

To clarify, do you mean substitute the benzylic OH with Cl, i.e. to make this:

I have tried with thionyl chloride but i have not been successful

Conditions? What happened?

I suggest a literature search. This compound is commercially available, so I expect there are published methods for its preparation.

[juaner]

Hello, i am trying to chlorinate the hydroxyl groups of the mandelic acid.

To clarify, do you mean substitute the benzylic OH with Cl, i.e. to make this:

I have tried with thionyl chloride but i have not been successful

Conditions? What happened?

I suggest a literature search. This compound is commercially available, so I expect there are published methods for its preparation.

Hello, i am trying to chlorinate the hydroxyl groups of the mandelic acid.

To clarify, do you mean substitute the benzylic OH with Cl, i.e. to make this:

I have tried with thionyl chloride but i have not been successful

Conditions? What happened?

I suggest a literature search. This compound is commercially available, so I expect there are published methods for its preparation.

I want all the hydroxyls are replaced by chlorine. The boiling point of the product is 120 degrees celsius, but i have tried with fractional distillation and i just had a yield of 10 percent.

[pgk]

What was the molar ratio of SOCl2 per mandelic acid (considered as a mixture of acid and alcohol)?
In practice, you need a quite higher molar ratio than theoretical, because the following side reaction is also favorable.
SOCl2 + 2 ROH → (RO)2SO + 2 HCl

[juaner]

What was the molar ratio of SOCl2 per mandelic acid (considered as a mixture of acid and alcohol)?
In practice, you need a quite higher molar ratio than theoretical, because the following side reaction is also favorable.
SOCl2 + 2 ROH → (RO)2SO + 2 HCl

I found in the literature that they used a ratio 1:3 (mandelic acid, SOCl2) with cyclohexane but they did not specify how they purify the product.

[pgk]

Did you try distillation under vacuum?
Remember that although rare to secondary alkyl chlorides, E1 elimination of the benzylic chloride might occur under strong acidic conditions, in presence of HCl byproduct and neighboring with an aromatic ring. So,  try to keep the lowest distillation temperature as possible.

[pgk]

According "Vogel’s textbook of practical organic chemistry", you need alcohol/SOCl2 1/3 molar ratio in order to achieve a yield = 50-60% of alkyl chloride and diol/SOCl2 1/4 molar ratio in order to obtain a dichloride (all of the exemples were primary alcohols and diols) and acid/SOCl2 1/1.5 molar ratio in order to achieve a yield = 70-75% of acyl chloride.
In other words and given that there is a secondary hydroxyl group, you need  at least mandelic acid/SOCl2 1/5 molar ratio and even higher, in order to achieve a yield = 40 45% maximum of benzylchloroacetoyl chloride. 

[juaner]

Thank you man. I am gonna try a ratio 1:8 and i will tell you the results.

[pgk]

It seems too much. Try 1/6 at the beginnings.