lab 2-quiz 1

Question 1

why was cold di water added to reaction mixture after ten minutes?

Answer 1

at high temps, acetanilide dissolves in water readily, but not at low temps. if hot water was used, product would dissolve and you couldnt obtain crystals for filtration.

Question 2

why was crude product recystalizzed?

Answer 2

remove impurities

Question 3

what is the purpose of acetic acid?

Answer 3

acetic acid polarizes the br-br bond. results in electrophilic Br+. the electrophile is attracted towards negative charge on acetanilide.

Question 4

why was 50% aqueous ethanol, not hexane used for recrstalization?

Answer 4

hexane is a nonpolar solvent, and is ideal for non polar compounds. aqueous ethanol is polar and ideal for dissolving polar compounds. P-bromoacetanilide is soluble in ethanol at room temp. so aqueous ethanol is used to recrystallize the product.

Question 5

Why is it uncenessary to include an aluminum trihalide in the electrophilic aromatic bromination reaction of acetanilide with molecular bromine?

Answer 5

the amide group is an activating group which increases electron density over ortho and para position. activated by amide group, so its not needed. its only for meta positions.

Question 6

the major organic product of this reaction is p-bromoacetanilide. explain why regioisomeric products are formed to a lesser extent.

Answer 6

for the meta product, you have to add ALCL3

Question 7

Why was the Hirsch funnel, nut Buchner funnel, used to collect the crystalline product?

Answer 7

bc we’re not making a lot of product. theres a leftover of protein. bromine is corrosive.