Riemann Reaction Mechanism:

Riemer reaction mechanism is nine step mechanism which are as followa;

Step(01):

In this step base (OH) attacks on chloroform and deprotonated chloroform 

step(02):

In this step deprotonated chloroform remove chloride ion  and give  dichlorocarbene.

Step(03):

In this step dichlorocarbene act as electrophile. Phenoxide ion act as nucleophile and attack on dichlorobenzene.

Step(04):

In this step shifting of hydrogen takes place

 step(05):

In this step oxygen share its lone pair to carbon by removing a chloride ion.

Step 06

In this step base attack on the product which are produced in step 05.

Step(07):

In this step oxygen give its lone pair to carbon by removing chloride ion as follows;

Step(08):

In this step attack of base takes place again.

Step (09):

In this step removal of water takes place and give o-hydroxy benzaldehyde or salicylaldehyde.

Riemann Reaction Mechanism:

Riemer reaction mechanism is nine step mechanism which are as followa;

Step(01):

In this step base (OH) attacks on chloroform and deprotonated chloroform 

step(02):

In this step deprotonated chloroform remove chloride ion  and give  dichlorocarbene.

Step(03):

In this step dichlorocarbene act as electrophile. Phenoxide ion act as nucleophile and attack on dichlorobenzene.

Step(04):

In this step shifting of hydrogen takes place

 step(05):

In this step oxygen share its lone pair to carbon by removing a chloride ion.

Step 06

In this step base attack on the product which are produced in step 05.

Step(07):

In this step oxygen give its lone pair to carbon by removing chloride ion as follows;

Step(08):

In this step attack of base takes place again.

Step (09):

In this step removal of water takes place and give o-hydroxy benzaldehyde or salicylaldehyde.