Question

8. After the glucose ring opens, an isomerization occurs to convert the al enediol intermediate shown (2). Show "arrow pushes on structure (1) which will which convert it to dohexose (1) into a ketohexose (3) via the common structure (2), and pushes" on structure (2) which will convert it to structure (3). (Use "B:" to deprotonate and "H-B" to protonate). o-H C-o-H it CI) 2. 9a. The key step in the catabolism of glucose is a retro-aldol condensation of the diphosphate shown below. Cirele the hydrogen which would have to be removed to induce this reaction, and show the "arrow push" which breaks the six carbon chain into two three-carbon pieces. Draw both of the products of this step : Base b. Why is the isomerization in question 8 necessary to allow the retro-aldol condensation in 9a to occur?

Answer 1

Answer: (8) In structure 1 , there is CO at 1st position and there is H and OH at alpha position , for conversion of 1st structure to 2nd , Base (B:) will abstract H⁺ from the alpha position and simultaneously carbon carbon double bond will form followed by protonation of C=O by H-B .

Conversion of (2) structure to (3) , Now base (B:) will abstract H⁺ from the enol OH which on rearrangement give structure (3) . So, (1) to (3) is the conversion of aldose to ketose .

(Arrow pushing mechanism is shown in the image attached)

Answer (9) : Base (B:) will abstract beta H (marked in image) to initiate retro aldol reaction , due to this retro aldol ,one molecule of glyceraldehyde phosphate and one molecule of carbanion generated , this carboanion is stabilized by resonance which on rearrangement give acetone hydroxy phosphate molecule .(structure of both the product obtained is shown in the image attached)

Answer 9(b): To allow retro aldol consedation in 9(a) , isomerisation in question (8) is necessary because after isomerisation of (1) structure of 8 , ketone will come at 2nd position , which is electron withdrawing group and can stabilize carbanion generated after attack of base onto beta hydroxy H , due to enolate formation , reaction speed up and 2 molecule both containing equal carbon can be generated.

M-C ot k-0-t-ㄧㄣ A: ぐこ: O Cori 2 Bast YA eH Ht + 1 2. Js+ Ind RessAldof