General
IUPAC name D-Glucose and β-D-glucopyranose
Synonyms
(2R, 3S, 4R, 5R) -2,3,4,5,6-pentahydroxyhexanal and (2R, 3R, 4S, 5R, 6R) -6 – (hydroxymethyl) oxane-2 ,3,4,5-tétrol
D-Glc and β-D-Glcp
Dextrose
Cerelose
CAS # 50-99-7 (L-Glc)
921-60-8 (α / β-L-Glcp)
EINECS No 200-075-1 (D-Glc)
213-068-3 (L-Glc)
218-914-5 (D-Glc)
PubChem 107526 (D-Glc)

5793 (α / β-D-Glcp)
79025 (α-D-Glcp)
Appearance white powder taste sucré.1
Chemical Properties
Formula C6H12O6 [isomers]
Molar mass 180.1559 g ∙ mol-1
C 40%, H 6.71%, O 53.29%
Physical properties
T ° C 146 ° fusion (α, D), 150 ° C (β, D)
Solubility in water (470 g.L-1).
Density (water = 1): 1561
Thermochemistry
ΔfH0solide -1273.3 kJ.mol-1
Precautions
SIMDUT2
Not controlled
[+]
Inhalation Cough.
Eyes Redness.
Ecotoxicology
LogP -3.31
SI units & CNTP unless otherwise noted.

Glucose is a aldohexose, principal representative of oses. By convention, it is symbolized by Glc.

It takes the form of a white powder, a sweet caramelized flavor from 150 ° C. It is soluble in water, ethanol and pyridine, but insoluble in diethyl ether and organic solvents.

Etymology

In 1838, a committee of the Academy of Sciences decided to draw the common grape sugar to starch, diabetes and honey called glucose, providing as the Greek etymology gleukos, sweet wine. Émile Littré, giving another etymology, the word glukus (taste sweet), with two upsilon (Greek i), the usual prefix became Glyce, as in glucose, glycogen, etc. …

Structure

Glucose (dextrose synonymous when it comes to D-glucose) is a simple dare and more particularly a aldohexose. It has the same formula as its isomers, in particular mannose or fructose C6H12O6. The molar mass of glucose is 180.156 g.mol-1.

Figure 1: D-glucose in Fischer projection

Figure 2: Representation “chair” of the α-D-glucopyrannose

Its structural formula is shown in Figure 1. It contains an aldehyde, it is a carbohydrate reducer. Glucose is a polar molecule (with its pure lines), so it is soluble in water. It is thermodégradable and dialysis (see dialysis).

Glucose crystallizes pyran form. It is called glucopyrannose (Figure 2 and 3).

Figure 3: Representation of Haworth D-glucopyrannose

Figure 4: Three-dimensional representation (red: oxygen, gray: carbon, white: hydrogen).

Metabolism

Unlike sucrose, it is directly assimilated by the body, which is an essential fuel, including the brain. The energy contained in one mole of glucose is 2 871 kJ (or 686 cal) (1cal = 4.2 KJ).

New medical imaging techniques provide an assessment of the topology of cellular metabolism. In positron emission tomography is used for this compound derived from glucose: the 18F-fluorodeoxyglucose or FDG, which, from a structural, is close enough glucose to be picked up by the cells but useless in their metabolism. This compound is radioactive radiation are collected and, depending on their distribution in the body, produce an image of hyperfixation in places of high metabolism (eg the brain, heart, tumors …).

Sweetness

Glucose tablets

Glucose has a low sweetness, from 70 to 75. In contrast, the sucrose is 100 (by convention), it is much less used it in the food industry for its organoleptic qualities. It is rather used as a load (monohydrate crystalline form of syrup or concentrate) and is also present in the glucose syrups and glucose-fructose. It is also added in some products found on the market (eg in the dextro energy).

Optical properties conformers of D-Glucose
Linear projection Haworth

0.5%
α-D-Glucofuranose
<0.5%
β-D-Glucofuranose
<0.5%

α-D-glucopyranose
35%
β-D-glucopyranose
65%

Like all oses, glucose has asymmetric carbons. They are the number of 4 (numbers 2, 3, 4 and 5) 3 and give a power rotation (glucose is said optically active), ie it is able to divert the plane of polarized incident light. The stereoisomers of the natural glucose is D-Glucose (see chirality).

Solutions of pure α-D-glucopyrannose and β-D-glucopyrannose respectively power rotation of 112.2 ° and 18.7 ° (in solution in water at 20 ° C). However, these solutions are not stable and a balance is quickly tautomère with the following composition:
35% α-D-glucopyrannose
65% of β-D-glucopyrannose
0.5% D-glucose linear

The optical rotation is therefore 52.7 °. Which is positive, the D-glucose is clockwise.

Chemical properties

Crystallization

Concentrated solutions of glucose (> 30%) spontaneously crystallize at room temperature. Glucose in crystalline form, is sold as “dextrose” to avoid confusion with the glucose syrup, and is in the form monohydrate. Dextrose solutions are industrially produced by a total starch hydrolysis of starch. Hydrolysis is performed by hot-enzyme systems combining alpha and beta amylases.

Reactions in acidic media

In the presence of dilute acid, glucose does not react, it is a dare, it is not hydrolyzable.

In the hot concentrated acid, glucose undergoes dehydration and condensation with α-naphthol (Molisch reagent), which colors. Glucose crystallizes.

Alkaline

Ammonia accelerates the mutarotation.

In the presence of soda diluted, there is formation of a ènediol (unstable) that produces (Figure 5):
Fructose by isomerisation;
Mannose by épimérisation.

Figure 5: isomerization reaction / épimérisation glucose.

In an alkaline medium, glucose is oxidized. These reactions are complex and non-stoichiometric (assay by the method of Bertrand).

Properties of aldehyde
The reduction of glucose gives sorbitol;
The oxidation of glucose to give gluconic acid.

Glucose is a carbohydrate reducer, it is able to reduce
metal ions:
The mercury ion II (reaction Baudoin-Lewin): Hg2 + + Hg + → Glc oxidation products;
The iron ion III (reaction Hagedorn-Jensen): Fe3 + + Fe2 + → Glc + oxidation products;
The silver ion (Tollens reaction): Ag + + Ag + → Glc oxidation products;
The copper ion (reaction of Fehling): Cu2 + + + Cu2O Glc → oxidation products.
Organic compounds:
the 3.5-dinitrosalicylate (yellow compound) is reduced by 3-amino-5-nitrosalicylate (red) allows the determination of glucose and other carbohydrates reducers.

Fehling’s reaction is used in the method of Bertrand. The precipitate of copper oxide redissous II is then determined.

Properties of the primary alcohol function

This function is carried by carbon No. 6, oxidation gives glucuronic acid aldehyde if the function has been protected by combining it with something else.

Nitric acid oxidizes the hot terminal of the two functions of glucose carbon 1 and 6 and form an acid Aldara (diacid carboxylic) acid glucarique.

Determinations of glucose

Polarimetry

Glucose with an optical rotation may be determined by polarimetry. The optical rotation of a solution is proportional to the concentration of glucose.

This method is used in medicine, diabetics control their blood glucose by this method.

Refractometry

This method consists of measuring the refractive index of a sugar solution with a refractometer, knowing that the index depends on the concentration of sugar. This method is used in winemaking to measure the sugar content of grape juice.

Determination by the glucose oxidase

This enzymatic method uses an enzyme (Figure 6): glucose oxidase (derived from Aspergillus niger). Glucose is oxidized by the oxygen in the air gluconolactone (gluconic acid can) with production of hydrogen peroxide. The latter is in fact determined by colorimetry. In the presence of a peroxidase, it reduces oxide chromogen whose absorbance is measured with a spectrophotometer. The chromogen may be phenol and the 4-aminophénazone oxidized to quinone-imine. In other techniques, hydrogen peroxide is oxidized at an electrode (the current produced is proportional to the concentration of glucose).

Figure 6: Determination of glucose by glucose oxidase.

This method is used in medical biochemistry to measure glucose in plasma.

Quote

“It’s a beautiful ring structure, an almost regular hexagon, which is subject to trade balance and difficulty with the water in which it is dissolved (…) And if somebody really wanted to ask: why ring and why soluble in water, well, it tranquiliser, these are the issues, not very many, that our science is able to respond. “Primo Levi, The periodic table, 1975.

Shared Post