The simple carbohydrates and the glucosides / by E. Frankland Armstrong.

  • Edward Frankland Armstrong
Date:
1910
Catalogue details

Licence: In copyright

Credit: The simple carbohydrates and the glucosides / by E. Frankland Armstrong. Source: Wellcome Collection.

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    CHAPTER I. GLUCOSE (DEXTROGLUCOSE OR DEXTROSE). It has been customary to speak of this sugar as grape sugar, to distinguish it from cane sugar, and on account of its occurrence in the juice of the grape and of other ripening fruits in association with fructose (laevulose); the two hexoses are probably derived from pre-existent cane sugar, as the three sugars are nearly always found together and cane sugar is easily resolved into glucose and fructose by hydrolysis . CijHjjOu + h20 = c6h12o6 + c6h12o6 Cane sugar. Glucose. Fructose. Glucose is also formed from other more complex sugars when these are broken down by hydrolysis with the assistance of the appropriate enzymes or of acids—for example, from milk sugar or lactose, malt sugar or maltose, starch and cellulose. It is easily prepared from starch by the action of diluted sulphuric acid and is therefore to be purchased at small cost. It separates from an aqueous solution with a molecule of water of crystallisation, but this is held only loosely, as the anhydrous substance may be crystallised from dilute alcohol. Unlike cane sugar, it never separates in well-defined clear crystals from either water or alcohol, but is usually met with as crystalline powder. Constitution of Glucose.—Glucose is represented by the molecular formula C6H1206. Five of the six atoms of oxygen are to be regarded as present in the alcoholic form, as hydroxyl (OH); the sixth under certain conditions manifests aldehydic functions. Thus, when acted upon by metallic hydroxides, glucose forms compounds which re- semble the “ alcoholates ”; and it is converted by acids, acid oxides and chlorides, into ethereal salts or esters such as the following:— C6H70(N03)5 c6h70(0 . co . ch3)5 C6H70(0 . co . c6h5)8 Glucose pentanitrate. Glucose pentacetate. Glucose pentabenzoate. On reduction, it takes up two atoms of hydrogen and is converted into a hexahydric alcohol; on oxidation it yields the monobasic acid, gluconic acid, C5H6(OH)5. CO . OH ; when heated with a concentrated solution of hydrogen iodide, it loses the whole of its oxygen and is converted into an iodohexane C6H13I, which itself is a derivative of normal hexane, CH3. CH2. CH2. CH2. CH2. CH3. On account of the stability of glucose, it is to be assumed that each *
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