[venkatjohnny]

Hi,
i'm doing aldehyde protection using trimethyl orthoformate in the first step of my project. I'm not getting the mechanism for this reaction, can any one plz help me to figure out the proper mechanism.
chemicals:4-formyl nitrobenzene(starting material), trimethyl orthoformate & para-toluene sulfonic acid.
solvent: methanol

[Dan]

You should look up acetal formation and hydrolysis as it's an important mechanism to be aware of.

The trimethyl orthoformate is acting as a drying agent. One equivalent of water is formed in acetal formation, and this is consumed in the hydrolysis of trimethyl orthoformate to methyl formate (and possibly on to formic acid).

Notice the entire process is reversible in acid, so the cosumption of water drives the equilibrium to the product side. If you treat an acetal with aqueous acid it will be hydrolysed back to the aldehyde via the reverse pathway. Acetals are generally stable in aqueous base though.

I have proposed a quick mechanism below, proton transfers etc are not shown in full detail.