Chapter 25 Carbohydrates 25 1 Classification of Carbohydrates
Chapter 25 Carbohydrates
25. 1 Classification of Carbohydrates
Classification of Carbohydrates monosaccharide disaccharide oligosaccharide polysaccharide
Monosaccharide is not cleaved to a simpler carbohydrate on hydrolysis glucose, for example, is a monosaccharide
Disaccharide is cleaved to two monosaccharides on hydrolysis these two monosaccharides may be the same or different C 12 H 22 O 11 + H 2 O sucrose (a disaccharide)
Disaccharide is cleaved to two monosaccharides on hydrolysis these two monosaccharides may be the same or different C 12 H 22 O 11 + H 2 O sucrose (a disaccharide) C 6 H 12 O 6 + C 6 H 12 O 6 glucose (a monosaccharide) fructose (a monosaccharide)
Higher Saccharides oligosaccharide: gives three or more monosaccharide units on hydrolysis polysaccharide: yields more than 10 monosaccharide units
Table 25. 1 Some Classes of Carbohydrates No. of carbons Aldose Ketose 4 Aldotetrose Ketotetrose 5 Aldopentose Ketopentose 6 Aldohexose Ketopentose 7 Aldoheptose Ketoheptose 8 Aldooctose Ketooctose
25. 2 Fischer Projections and D-L Notation
Fischer Projections
Fischer Projections
Fischer Projections of Enantiomers
Fischer Projections of Enantiomers
Enantiomers of Glyceraldehyde CH H D O OH CH 2 OH (+)-Glyceraldehyde CH HO L O H CH 2 OH (–)-Glyceraldehyde
25. 3 The Aldotetroses
An Aldotetrose 1 H H CH 2 3 4 O OH OH CH 2 OH stereochemistry assigned on basis of whether configuration of highest-numbered stereogenic center is analogous to D or L-glyceraldehyde
An Aldotetrose 1 H H D CH 2 3 4 O OH OH CH 2 OH stereochemistry assigned on basis of whether configuration of highest-numbered stereogenic center is analogous to D or L-glyceraldehyde
An Aldotetrose 1 H H CH 2 3 4 O OH OH CH 2 OH D-Erythrose
The Four Aldotetroses CH H H O OH OH CH HO HO O H D-Erythrose and L H -erythrose are enantiomers CH 2 OH D-Erythrose L-Erythrose
The Four Aldotetroses CH H H O OH OH CH 2 OH D-Erythrose CH HO H OH CH 2 OH D-Threose D-Erythrose and D-threose are diastereomers
The Four Aldotetroses CH O CH HO HO H H CH 2 OH L-Erythrose O H OH CH 2 OH D-Threose L-Erythrose and D -threose are diastereomers
The Four Aldotetroses CH D-Threose and L- threose are enantiomers HO H CH O H OH CH 2 OH D-Threose H HO O OH H CH 2 OH L-Threose
The Four Aldotetroses CH O CH H OH HO H H CH 2 OH D-Erythrose CH 2 OH L-Erythrose O H CH H OHHO CH 2 OH D-Threose O OH H CH 2 OH L-Threose
25. 4 Aldopentoses and Aldohexoses
The Aldopentoses There are 8 aldopentoses. Four belong to the D-series; four belong to the L-series. Their names are ribose, arabinose, xylose, and lyxose.
The Four D-Aldopentoses CH H O OH CH 2 OH D-Ribose CH H O OH CH 2 OH D-Arabinose CH H O OH CH 2 OH D-Xylose CH H O OH CH 2 OH D-Lyxose
The Four D-Aldopentoses CH O CH H OH H CH 2 OH D-Ribose O CH OH HO OH H CH 2 OH D-Arabinose O CH H HO OH H CH 2 OH D-Xylose O H OH CH 2 OH D-Lyxose
The Four D-Aldopentoses CH O H OH HO H H OH HO OH H H OH CH 2 OH D-Ribose CH 2 OH D-Arabinose CH 2 OH D-Xylose CH 2 OH D-Lyxose
The Four D-Aldopentoses CH O H OH HO H H OH HO OH H H OH CH 2 OH D-Ribose CH 2 OH D-Arabinose CH 2 OH D-Xylose CH 2 OH D-Lyxose
Aldohexoses There are 16 aldopentoses. 8 belong to the D-series; 8 belong to the L -series. Their names and configurations are best remembered with the aid of the mnemonic described in Section 25. 5.
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