1559rch24423-43810/20/054:54MPag0428 EQA 428 chapter 24 CARBOHYDRATES:POLYFUNCTIONAL COMPOUNDS IN NATURE HOCH CH2OH OH CH.OH d HO CH,OH B a-Pvr B CH2OH HO OH OH HO OH HO o-Pyran 36.No.They are all hemiacetals and therefore are capable of readily interconverting their and B HO CH.ON 37.(a) (b)HO OH OH HooH@H今0 OH OH (d)isan unusual case where the CH,OH is forced to be axial to allow all four OH's to be equatorial. 38.Base-catalyzed llows the interconversion to take place.But notice that the product is no sor the ng a pro the original ketone or the isomeric aldehyde. CHOH HC-OH HC-OH -OH HC-Q HC-0 )ther er(d) (e) 36. No. They are all hemiacetals and therefore are capable of readily interconverting their and
anomers. 37. (a) (b) (c) (d) (d) is an unusual case where the CH2OH is forced to be axial to allow all four OH’s to be equatorial. 38. Base-catalyzed enolization allows the interconversion to take place. But notice that the product is not an ordinary enol. It has hydroxy groups on both carbons of the double bond: It is an enediol. Therefore, when it tautomerizes it has the option of losing a proton from either of two hydroxy groups, giving either the original ketone or the isomeric aldehyde. Aldose Other enolate H2O OH H2O OH OH HC O HC OH HC O C  OH HC O C O O CH2OH C Ketose Enolate Enediol H2O OH H2O OH CHOH C   HC C OH OH HC OH O O C HO O HO OH OH CH2OH HOCH2 O HO HO OH OH CH2OH O HO HO OH OH O HO OH OH OH OH -Furanose -Pyranose OH O HO HO OH HO O CH2OH CH2OH
OH CH2OH OH CH2OH HOCH2 HO H
OH CH2OH OH OH OH HOCH2 CH2OH -Furanose O
-Pyranose CH2OH HO OH OH OH O CH2OH OH
CH2OH OH 428 • Chapter 24 CARBOHYDRATES: POLYFUNCTIONAL COMPOUNDS IN NATURE 1559T_ch24_423-438 10/20/05 4:54 AM Page 428