Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

-The product contains appreciable unreacted Br 2 -The reaction product was incom

ID: 900047 • Letter: #

Question

-The product contains appreciable unreacted Br2

-The reaction product was incompletely recrystallized

-The trans-cinnamic acid did not appreciably react with Br2

The reaction of trans-cinnamic acid with Br2 yields the dibromide product 2,3-dibromo-3-phenylpropanoic acid. Select the consequence that is LEAST likely to occur if the dibromide product is recrystallized in dichloromethane, rather than a solution of 50% aqueous ethanol.

-The dibromide product may not completely recrystallize

-The reaction would occur as a syn addition, rather than an anti addition

-Residual acetic acid will not dissolve into the recrystallization solvent

-The recrystallization in dichloromethane would need to be performed at a lower temperature than it could be in 50% aqueous ethanol

omine was added to trans-cinnamic acid and the melting point range of the purified product was found to be 135-136 "C. Based on the melting points in the table below, select the most likely reason for this result. COOH Br Compound melting point, OOH trans-cinnamic acid 136 Br -7 Br2 erythro-2,3-dibromo-3- 204 phenylproapnoic acid threo-2,3-dibromo-3- 95 phenylproapnoic acid acetic acid 2,3-dibromo-3 phenylpropanoic acidP trans-cinnamic acid

Explanation / Answer

-----The product is a mixture of erythro and threo isomer.

-----The recrystallization in dichloromethane would need to be performed at a lower temperature than it could be in 50% aqueous ethanol