Dolbier HW Solutions 612

Dolbier HW Solutions 612 - 706 CARBOHYDRATES Of the two...

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Of the two chair conformations of b - L -ribose, the one with the greater number of equatorial substituents is more stable. 25.7 The equation describing the equilibrium is Let A 5 percent a isomer; 100 2 A 5 percent b isomer. Then A ( 1 29.3 ° ) 1 (100 2 A )( 2 17.0 ° ) 5 100( 1 14.2 ° ) 46.3 A 5 3120 Percent a isomer 5 67% Percent b isomer 5 (100 2 A ) 5 33% 25.8 Review carbohydrate terminology by referring to text Table 25.1. A ketotetrose is a four-carbon ke- tose. Writing a Fischer projection for a four-carbon ketose reveals that only one stereogenic center is present, and thus there are only two ketotetroses. They are enantiomers of each other and are known as D - and L -erythrulose. 25.9 ( b ) Because L -fucose is 6-deoxy- L -galactose, f rst write the Fischer projection formula of D -galactose, and then transform it to its mirror image,
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