A textbook of biochemistry for students of medicine and science / by A.T. Cameron.
- Alexander Thomas Cameron
- Date:
- 1938
Licence: In copyright
Credit: A textbook of biochemistry for students of medicine and science / by A.T. Cameron. Source: Wellcome Collection.
94/454 page 78
![rotation of -f- 52-5° at 20° C. Because it is dextro-rotatory the term dextrose is often used for it. It has the formula CH2OH .CHOH . CHOH . CHOH . CHOH . CHO with four asymmetric carbon atoms (marked by asterisks). Using the projection method illustrated for lactic acid in Chapter II., its space formula can be derived in the following manner. The one-plane configuration of the carbohydrates is now based on their relationship to glycerose, the simplest sugar to possess an asymmetric carbon atom. It possesses but one, and the hydroxyl group attached to it is arbitrarily written on the right for the dextro- compound. CHO , I H—C—OH I ch2oh All sugars derivable from d-glycerose are termed dextro-sugars, whatever their rotation, and all derived from Z-glycerose are termed laevo-sugars. The relationship between d-glycerose and d-glucose, all the steps of which have been clearly traced and proved, is shown below : CHO CHO H—C—OH CHO HO—C—H HO—C—H CHO II—A—OH H—A—OH H—A—OH II—C—OH -> H—A—OH -> II—C—OH -* H—A—OH I I I I gh2oh ch2oh ch2oh ch2oh d-Glycerose d-Erythrose d-Arabinose d-Glucose The Oxide (Lactone) Structure of Glucose. We have not yet, however, arrived at the true configuration of most of the molecules of glucose in solution. When crystalline glucose is dissolved in water it is found that the optical rotating power of the solution changes for many hours, sometimes increasing, but more usually decreasing, until finally that equilibrium is reached for which [a]D = + 52-5°. This phenomenon of changing rotation has been called muta- rotation (L. mutare, to change). Such an effect at once suggests that there are present in the](https://iiif.wellcomecollection.org/image/b2992859x_0094.jp2/full/800%2C/0/default.jpg)
