1559T_eh24423-43810/20/054:54 M Page436 436 chapter 24 CARBOHYDRATES:POLYFUNCTIONAL COMPOUNDS IN NATURE H CH2OH SC.Co CH,OH C=0 C=0 +H- -OH CCHOH CHOH CHOH 9H,0 CH2OH CH2OH C=0 C=0+C0 dendroketose CH-OH CHOH CH2OH (b)The hint is supposed to make you think about enolate ions.Glyceraldehyde and 1.3-dihydroxy-propanone are readily interconverted in aqueous basic solution via enolates and enols CH.OH CHOH CHOH HC-0H- C-oH脸 CH-OH CH-OH Enolat Enol HC=0 CHO -0H:C-0H CHOH CH2OH CH2OH Enolate aqucous basc,for example.We saw this same mechanism in Problem 38. 56.(a)Br2.H2O:(b)see answer to Problem 40b:(c)CH3OH,H":(d)ester of acid in (b):-COOCH3 at the top;(e)forms the amide:-CONH2 at the top.Then CONH NH CHO O OH HO- H 一H Br2.NaOH CO2 HO H -OH -OH CH2OH (e) Ruff degradations.55. (a) Aldol condensations! Abbreviated mechanisms are shown below. Refer to Section 18-6 for more details, if necessary. (b) The hint is supposed to make you think about enolate ions. Glyceraldehyde and 1,3-dihydroxy-propanone are readily interconverted in aqueous basic solution via enolates and enols. So a basic solution of either one rapidly becomes a mixture of the two, and the reactions in (a) can then occur. This aldose yz ketose interconversion is general. Glucose and fructose are interconverted by aqueous base, for example. We saw this same mechanism in Problem 38. 56. (a) Br2, H2O; (b) see answer to Problem 40b; (c) CH3OH, H; (d) ester of acid in (b): OCOOCH3 at the top; (e) forms the amide: OCONH2 at the top. Then The hydroxyamine (f) readily loses NH3 on the heating to give the aldehyde. This sequence achieves the removal of Cl from an aldose to form a new aldose with one less carbon, just like the Wohl and Ruff degradations. Br2, NaOH Hofmann degradation  NH3 CONH2 (e) CO2 (f) D-Threose (g) CH2OH OH HO H H OH H NH2 CH2OH OH HO H H OH H CHO CH2OH HO H H OH Enolate CHO CH2OH CHOH HC O  H OH CH2OH C HC O CH2OH OH C OH CH2OH CH2OH Enolate Enol C O  CHOH CH2OH C O CHOH HC CH2OH C O HO H OH HO HO CH2OH C OH O H CH2OH CH2OH CH2OH CH2OH C O CH2OH CHOH C C O O dendroketose HO CH2OH CHOH C O CH2OH CHOH C O C H O D-sorbose and D-fructose mainly H HO CH2OH H OH 436 • Chapter 24 CARBOHYDRATES: POLYFUNCTIONAL COMPOUNDS IN NATURE 1559T_ch24_423-438 10/20/05 4:54 AM Page 436