By J. Aehlert (Auth.)
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Extra info for Chemistry of the Carbohydrates
H u d s o n . According to this system, for sugars of t h e D-series t h e more dextrorotatory isomer of each a-ß pair is kno\vn as t h e alpha isomer ; t h e lesser dextrorotatory isomer is the b e t a isomer. For sugars of t h e L-series, t h e converse is t r u e . , t h a t t h e y differ only in t h e configuration of t h e hemiacetal carbon a t o m s . If t h e compounds being considered m u t a r o t a t e a n d are of t h e D-series, usually t h e α-isomer is t h e form which m u t a r o t a t e s t o a value less positive t h a n the initial value.
1. As shown in I a n d I I , four of the a t o m s of the ring m a y lie in one plane, a n d - t h e other two a t o m s m a y lie on t h e same side of t h e plane as in I I . T h e s t r u c t u r e represented in I I is t h e eis or b o a t t y p e ; t h a t in I is t h e trans or chair t y p e of structure. T h e " s t r a i n e d " coplanar t y p e of structure is represented in V. T h e structures represented in I I I a n d I V have five ring-atoms in one plane a n d t h e sixth a t o m projects below t h e plane of t h e 25 other atoms.
2) Glucose a n d mannose are oxidized b y nitric acid t o dibasic acids which are different a n d which are b o t h optically active. COOH CHO I (CHOH)4 I HNO, I (CHOH)4 C H 2O H COOH griwco-Saccharic acid Glucose CHO I (CHOH)4 COOH HNOa (CHOH)4 I I C H 2O H COOH Mannose wawio-Saccharic acid T h e optical activity of t h e products proves t h a t the configuration of t h e asymmetric a t o m s (carbon a t o m s 2 to 5) cannot be of t h e t y p e which produces internal compensation. (3) L-Arabinose, which h a d been isolated from beet pulp b y Scheibler in 1868 a n d shown to be an aldopentose by Kiliani in 1887, reacts with H C N with t h e production of a nitrile which hydrolyzes to a six-carbon monobasic acid ( I ) .