(a) Which of the aldopentoses (Figure 24-1) would give optically active alditols upon reduction with NaBH₄? 

(b) Using d-fructose, illustrate the results of NaBH₄ reduction of a ketose. Is the situation more complicated than reduction of an aldose? Explain. 

Figure 24-1

Transcribed Image Text:

CHO Figure 24-1 D-Aldoses (up to the aldohexoses), their signs of rotation, and their common H- -ОН CH,OH names. CHO CHO D-(+)-Glyceraldehyde но- -он H- Но- -H H- H- -OH CH,OH CH,OH D-(-)-Erythrose D-(-)-Threose CHO CHO CHO CHO H HO- Но -H H -ОН HO -H- H. OH H- Но -H HO -H- FOH CH-OH H- FOH H- H FOH H FOH CHHOH CHHOH CHHOH D-(-)-Ribose D-(-)-Arabinоse D-(+)-Xylose D-(-)-Lyxose СНО CHO CHO CHO CHO CHO CHO CHO ОН НО -H- H ОН НО H- H- ОН Но- -H- H- ОН Но H- HO- H- OH Но- H- HO -H- H- HO- H- HO- HO Но H- H- HO- H- OH H- OH H- HO H но- Но Но H- H- -ОН H- -ОН H- -ОН H- -ОН H- -ОН H- Но- H- -ОН H- -O- CH2OH CH,OH CH,OH CH;OH CH,OH CH;OH CH;OH CHHOH D-(+)-Allose D-(+)-Altrose D-(+)-Glucose D-(+)-Mannose D-(-)-Gulose D-(-)-Idose D-(+)-Galactose D-(+)-Talose