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460 Chapter 24 CARBOHYDRATES: POLYFUNCTIONAL COMPOUNDS IN NATURE 42. Each carbon atom in the starting sugar is alongside its product after HIO, cleavage. The number of hydrogens on each carbon remains the same before and after cleavage. (a) CH₂OH H₂C=0 CO₂ that is, 2 formaldehyde + 1 CO₂ CH₂OH H₂C=0 (b) HC=0 HCO₂H that is. formic acid + 1 acetaldehyde HC-OH HC=0 CH₃ CH₃ (c) CH₂OH H₂C=0 that formic acid + 2 formaldehyde CH₂OH H₂C=0 43. (a) (i) COOH (ii) COOH (iii) CH₂OH H H H H OH H OH H OH CH₂OH COOH CH₂OH D-Threonic acid D-Tartaric acid D-Threitol (iv) COOH (b) (i) COOH (ii) H OH H OH H H OH H H OH H OH CH₂OH CH₂OH COOH phenylosazone* D-Xylonic acid acid