IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry

masmuu

please explain me the following observation:

R-OH + H-Cl gives R-Cl + H2O

but

R-OH + Na-Cl gives no rxn.

catch_arnnie

see, NaCl is a salt but ROH is a very weak acid, so, they can never react to give RCl.

moreover, always the weaker base exists in the medium.
if ROH reacts with NaCl then it should possibly give RCl + NaOH but NaOH is a strong base so, the reaction never happens as a weaker base i.e. Cl- is already present...

i hope you get the concept....

achman

this is based on leaving group tendency.

-Cl is a good leaving group while -OH is weak one.

A strong leaving group can substitute a weak leaving group while vice versa is not possible

to idintify a leaving group, simply make conjugate acid of that gp. A strong acid has weak conjugat base and so a strong leaving gp.

arun-rashi

in ROH there is very difficult nucleophilic substitution reaction due to very poor leaving group .in acidic medium they form protonated alcohol so intermediate is carbocation and they undergo substitution reaction .by reaction with NaCl no carbocation so no substitution while in acidic medium easy carbocation so easy substitution reaction.for done easy substitution in alcohol they are converted in tosyl group by reactiopn with tosyl chloride so easy substitution will takes place.

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