Nowadays, the synthesis of benzoic acids for example salicylates have become attractive due to their biological, pharmaceutical and industrial widely applications. In this project, the novel compounds, 1,4-dimethoxy-2-methyl benzene (47) , 1,4-dimethoxy-2,3-dimethyl benzene (48) , methyl-4-methoxy benzoate (49) , methyl-3-methoxy salicylate (50) , methyl-2,5-dimethoxy benzoate (51) , methyl-3-methoxy-5-methyl salicylate (52) , ) , methyl-2,5-dimethoxy-4-methyl benzoate (53) , dimethyl-3,6-dimethoxy phthalate (54) , methyl-4-(2,5-dimethoxy benzoyl)-2,5- dimethoxy benzoate (55) , methyl-2,4-dimethoxy benzoate (57), methyl-2,4-dimethoxy-5-methyl benzoate (58) , methyl-4-methoxy salicylate (59) , dimethyl-4,6-dimethoxy isophthalate (60) , trimethyl-5-carboxylate-4-hydroxy-2-methoxy-6-methyl isophthalate (61) , bis(2,6-dimethoxy phenyl)methanone (62) , methyl-3-(2,6-dimethoxy benzoyl)-2,4- dimethoxy benzoate (63) , bis(methyl-2,6-dimethoxy-3- benzoate)methanone (64) were synthesized . The Friedel-Crafts acylation reaction of electron rich arenes, 1,4-dimethoxy benzene (38) , 1,3-dimethoxy benzene (56) was used for synthesis this compounds with chloroformate acylating reagent. Also the use of appropriate catalyst has been investigated in Friedel-Crafts acylation reaction because of importance of green chemistry. For this propose aluminium chloride, ferric chloride (iron trichloride), silica supported aluminium chloride and etc were used.The different quantities of catalyst and different temperature condition were investigated for the optimization of reaction yield. The synthesized compounds were characterized by GC/MS, MASS, 1 H-NMR and FT-IR. In second part of this project, different methyl salicylated products derived from 1,4-dimethoxy benzene, 1,3-dimethoxy benzene and , 1,2-dimethoxy benzene were opted theoretically by performing HF, DFT and MP2 levels of theory using the standard 6-31G basis set. The energy barrier and stability of these compounds were compared. The total energy, relative energy and optimized geometries were calculated. The conformational analysis was done for methyl-3-methoxy salicylate (50) to study most stable and unstable conformer and intramolecular hydrogen bonding. In the next part, the several structures of tetrazoles and substituted imidoyl azides were opted by calculation methods to study the equilibrium and mechanism of the isomerization. Substituent effect was investigated on equilibrium of 1-tetrazole, 2-tetrazole and azide and their relative stability was compared. The calculated results were compared with the experimental findings. The calculated results indicate good agreement with the experimental results.