[kuromi]

benzene + CH3Al/AlCl3 ---> methyl benzene + CH3Al/AlCl3  --->
1,2 or 1,3 or 1,4-dimethyl benzene +KMnO4/H+ ---> benzene-1,2-dicarboxylic acid +
P2O5 --->  benzene-1,2-dicarboxylic anhydride  !!! 

does it work ??  if not , what is the other way which can carry out in school lab??   
 

[Momer]

I think this is the easiest and simplest way (Freidle Craft), there are other methods but they are other methods but they are complicated.

By the way, why you wrote CH3Al !!!! it should be alkyl halide CH3-X.

[kuromi]

I think this is the easiest and simplest way (Freidle Craft), there are other methods but they are other methods but they are complicated.

By the way, why you wrote CH3Al !!!! it should be alkyl halide CH3-X.

it should be CH3Cl ,  i wrote wrongly !!

i also have one question is that how to test the product is benzene-1,2-dicarboxylic anhydride ?

[Schrödinger]

Can benzene-1,3-dicarboxylic acid and benzene-1,4-dicarboxylic acid form anhydrides?

[orgopete]

If you are not going to purchase it from a supplier, I would do a F.C. acylation with succinic anhydride, cyclize, and then oxidize it to phthalic acid.

[kuromi]

Can benzene-1,3-dicarboxylic acid and benzene-1,4-dicarboxylic acid form anhydrides?

i think they can't form  anhydrides !!! 

[kuromi]

If you are not going to purchase it from a supplier, I would do a F.C. acylation with succinic anhydride, cyclize, and then oxidize it to phthalic acid.

your suggest may be worked ...  but i think it is complicated  and my original material is benzene .   

[Schrödinger]

Can benzene-1,3-dicarboxylic acid and benzene-1,4-dicarboxylic acid form anhydrides?

i think they can't form  anhydrides !!! 

Now that you are clear with the fact that there is only one benzene dicarboxylic anhydride (i.e, phthalic anhydride), what compounds do you know that can be formed from phthalic anhydride ?