Acetaminophen is another compound with these properties. Paracetamol or acetaminophen is a widely used over-the-counteranalgesic (pain reliever) and antipyretic (fever reducer). In combination with opioid analgesics, Paracetamol can also be used in the management of more severe pain such as post surgical pain and providing palliative care in advanced cancer patients. p - Anisidine ,this compound consists of a benzene ring core, substituted by one methoxy group and the nitrogen atom of an amine group in the para. The first part of this work is the study of friedel-crafts reaction and synthesis of several derivatives of thise compound which have properties of acetaminophen. The acetylation of amines, alcohols and phenols is an important chemical reaction in organic synthesis. In general, metal halides (AlCl 3 , FeCl 3 , etc.) or strong mineral acids are used as catalysts for aromatic acylation. In first part of this work the acylation of rich arene, anisole with mild reagent, acetylchloride and green Ionic liquid catalyst, 3-carboxy-piridinium hydrogen sulphate was done to produce selective products such as 4-methoxy-aceophenon,Then acylation of para anisidine with acylating reagent acetic anhydride to produce p -Anisidide and N-(3-acetyl-4-methoxy phenyl)acetamide was done. Also methyl formation of para anisidine with chloroformate to produce methyl 2-methoxy-5-(methoxy-carbonyl amino) benzoate was done,so the friedel-crafts acylation reaction of methoxy benzene and p -Anisidine was used with acetyl cholorid, chloroformate and acetic anhydride acylating reagent with or without present Ionic liquid. The development of heterogeneous catalysts like IL has played an important role, since they offer advantages such as clean reaction conditions, easy separation of the catalyst from the reaction medium, greater selectivity and generally give higher yield of products and can be recycled for a number of times, Also catalyst as aluminium tri chloride, alumina, ionic liquid (3-carboxy-piridinium hydrogen sulphate) and montmorilonite-k10 (activated with hydrochloric acid or sulfuric acid) were used and optimized condition in term of reaction time and temperature was studied. The synthesized compounds were characterized by elemental analysis, GC/MS, 1 H-NMR, 13 C-NMR and FT-IR. In theoretical part of this project, the effect of intramolecular hydrogen bonding, hyperconjugation and steric effect on [di-hydroxy, di-thiol and di-silyl] ethane were studied by performing HF, DFT and MP 2 levels of theory using 6-311++G** basis set. The total energy, steric energy and hyperconjugation effect and optimized geometries were calculated whith NBO analysis. For these derivatives of ethane, the conformational analysis was done to find the energy minima and maxima in different conformers.