Question

(5) During step 13 (TLC) of Part 4, a student switches the order of lanes 1, 2, 3 and 5. They are confident only in the identity of lane 4-the recrystallization filtrate. After running the TLC plate with 7:1 petroleum ether- diethyl ether, they obtain the following plate: А в с Lane 4: Recrystallization Filtrate (a) Assign A, B, C, and D to each of the following: initial crude product, triturant, solid after trituration, and purified triphenylmethanol. (b) Historically, most students have often observed curious results in Lane 4, the recrystallization filtrate, as shown above. Assuming that the isopropyl alcohol was not contaminated, propose an explanation for the observation. (C) Based on the TLC plate above, did the student lose any product during the trituration step? To the recrystallization step?

Answer 1

(a) A = triturate, B = Purified triphenyl methanol, C = Initial Crude, D = Solid after trituration.

(b) The lane 4, shows so many spots which can be attributed to other side products formed in small concentration or else impurities in the staring materials used during the reactions which makes the TLC pattern highly haphazard.

(c) As can be seen clearly from the TLC pattern, there is huge polarity difference between triturant and Purified triphenyl methanol, A = triturant clearly shows no loss of Purified triphenyl methanol during trituration step.However, in recrystallization there was a small loss of the product.