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BRANDEIS UNIVERSITY CHEMISTRY 29A PRELAB WRITEUP AND EXPERIMENTAL REPORT SHEET NAME_ T.A.’S NAME DATE_________ EXPERIMENT # __5_____ TITLE Alkylation of a benzene ring Purpose: to synthesize 1,4 di(1,1 dimethyl ethyl) 2,5 dimethoxy benzene by alkylation of a benzene ring PRELIMINARY WRITEUP* (INCLUDING EQUATIONS, TABLE OF MATERIALS, THEIR AMOUNTS AND CONSTANTS. AND PRELAB QUESTIONS. Place these questions on the reverse of this page) (* use reverse of both sheets if necessary) Substance Purpose Melting Point (Celsius) Molecular Weight (g/mol) Theoretical amount used (g) Other notes Water Removal of water soluble impurities from product, and crystallization N/A N/A N/A Methanol Used to remove impurities from product and as primary solvent for recrysallization (it dissolved the product at high temp and did not at low temp) N/A N/A As needed Density = 0.7918g/mL Sulfuric Acid Acts as lewis acid and reacts with alcohol to form 2-propyl carbocation intermediary N/A N/A 0.4mL Acetic acid Reaction solvent dissolves all reactants, protonates para dimethoxy benzene for easier electrophilic substitution N/A N/A 0.4mL 1,4 di(1,1 dimethyl ethyl) 2,5 dimethoxy benzene product 104-105 250.37 N/A 2-methyl 2 propanol Source of alkane for alkylation, reacts with sulfuric acid to product 2-propyl carbocation intermediary N/A 74.12 0.2mL Density = 0.79 g/mL 2-propyl carbocation Reactive intermediary attacks benzene ring and acts as electrophile in electrophilic substitution, attachment to benzene ring activates the ring N/A N/A In situ Highly reactive intermediary para dimethoxy benzene Source of aromatic ring, requires protonation to activate it for easier electrophilic substitution 57 138.16 .1182 EXPERIMENTAL PROCEDURES* (include in preliminary writeup) 1. dissolve completely 120 mg 1,4 dimethoxy benezene in 0.4mL acetic acid 2. warm gently, then add 0.2mL tert-butyl alcohol 3. cool in ice 4. add 0.4mL sulfuric acid dropwise 5. mix thoroughly, stir, allow solution to warm to room temperature 6. cool with ice, and add 2.5mL water dropwise 7. allow solid to crystallize 8. remove solution, and wash with water 9. determine crude weight 10. recrystallize solution from Methanol 11. cool solution, remove solvent and filter in Hirsch funnel 12. weigh product, and perform melting point analysis 13. perform IRs spectroscopy MODIFICATIONS AND OBSERVATIONS* (Obtained from the lab experience.)
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