Question

1. Calculate the overall yield for this 2-step reaction assuming the first and second steps had percentage yields of 50 % and 75 % respectively. (2 pts) - show calculations i r thiamine HNO3 thiamine → i OH HNO - 2. Circle the 'H NMR of Benzaldehyde. (2 pts) a) 3. What is the incorrect statement? (2 pts) When Benzaldehyde is converted to benzoin, a) The peak around 10 ppm in the H NMR is lost c)A peak around 3500 cm is appeared in the IR d)A chiral carbon is generated b) Total integration in the H NMR changes from 6 to 11 4. Select the most appropriate term. (2 pts) Thiamine is participated as a (reactant/catalyst/intermediate/product) in the conversion of benzaldehyde to benzoin.

Answer 1

thiamine 1 OH Step A stelle For steb?.. como of yield = 50%. a mole of benzaldehyde gives since a moles . compound caj gives 212 g of te, 2x 106 g of benzaldehyde preoduct (a). . Theoretical yield = 212 g Actual yield ling) . O since, if yield a - X (0 . Theoretical yield

0.5 50- = actual yield - x ..212 g 400 . => Actual yield = = = step 2: 0.52128 106 g For 212 g. of (a) gives 20. g. of (6) But, we have 106. g. of compound (b) [as Calaceated above) : 100g of (a) gives 210 x 106 g. of (b) for = 105.9 of (6) step (2) : : % of yield = 730%. :: Actual yield = 75x1059 = 78.75 g 100 calulation of over all % yield: 2 moles of benzaldehycle gives I mole product (6) of

So Theoretical yield of (b) = 210g Actual yield of 6) = 78.759 % % of vield - . Actual yield Theoretical yield X 100 78.759 x 100 210g = 37.5% Ans . 2 'H NMR for benzaldehyde :) . C e dn. 10 ppm (s, 1H) signals, due to Ha, Hy There should be four He h Hd prestons. f: Ha, Hbf HC A 6-8 ppm . can't be 'H NMR spectra. So, (a), (bif (d) for benzalotchyde correct option : ©

Analysis of "HNMR: fi 10 ppm ( ,141) 8: 7.6 pm ( d, Hel 7.7 ppm (2,2Hb) 8 ppm ( d, a Ha) "Incorrect statement is dj because there Chiral carbon in benzoini is no 5 : (No chircel caribesi) .. Correct option : © Thiamine : T I S (a biomoleculej 2 The amine is a persistent carbene which is used ! by enzyme to catalyze benzoin condensations in vivo. (Above reaction is benzoin condens. : -ation) Correct option! Thiamine as a catalyst.. STORE STOR