beta-D-Glucopyranose | C6H12O6 - PubChem
Glucose (also called dextrose) is a simple sugar with the molecular formula C6H 12O6. Glucose . From aqueous solutions, the three known forms can be crystallized: α-glucopyranose, β-glucopyranose and β-glucopyranose hydrate. celui d'amidon, celui de diabètes et celui de miel ont parfaitement la même composition. Beta-hexaclorociclohexano CONCLUSIONES Y RECOMENDACIONES OTRAS .. dechlorinated 36Cl-alpha-HCH during anaerobic incubation with glucose, There is a relationship between the concentrations in adipose tissue and que sur le mode d'action de l'alpha-HCH, de même que les tests de mutagénicité. Note that the other chiral centers in D-glucose define it as a “glucose” and not labeled as alpha or beta, depending on whether the hemiacetal -OH group is on .
The two different carbohydrate cyclic hemiacetal stereoisomers are called anomers and are labeled as alpha or beta, depending on whether the hemiacetal -OH group is on the same side of the ring as the terminal -CH2OH substituent beta anomer or on the opposite side alpha anomer.
The two anomers equilibrate in aqueous solution, a process known as mutarotation. The process is catalyzed by acid, since hemiacetal formation is catalyzed by acid. It exists in a six-membered ring cyclic hemiacetal form, as both an alpha and beta anomer. At equilibrium, the beta anomer of D-glucose predominates, because the -OH group of the anomeric carbon is in the more stable equatorial position of the more stable chair structure.
In alpha-D-glucose, the -OH group on the anomeric carbon is axial. Remember, for glucose, alpha is axial! Glucose is important because it represents the mobile source of energy for our cells. Through a variety of enzyme catalyzed reactions called metobolismglucose is oxidized, and the energy released from this process is used to provide energy for our cells. In other areas, for instance agricultural and greenhouse horticulture areas, the levels of the individual HCHs ranged from 0.
Concentrations of HCH isomers in solution and in suspension particle-bound in the Meuse and Rhine estuary were determined in The average concentrations of dissolved and suspended alpha-HCH were 20 and ng per litre, respectively.
Inthe concentration of dissolved alpha-HCH in coastal waters of the Netherlands was 0. Inthe levels of alpha-HCH were 0. However, a significant decrease was observed in the mids. When certain rivers in Yorkshire, England, were analysed for alpha-HCH inthe concentration varied from 0. Inthe highest value was 0. In Japan, 60 water samples were examined in and 0. Hamada and by T. The alpha-HCH concentrations varied from 0.
The mean concentrations varied in the different sampling stations from 0. Edelman analysed 96 samples of the upper 10 cm of the soil from 38 natural reserves in the Netherlands for alpha-HCH and gamma-HCH. Further pollution has been caused by the dumping of chemical waste and its use in the levelling of certain areas. From these dumping areas dispersal of the chemical waste can occur by leaching or wind erosion from open storage depots. In certain polluted areas, high concentrations of HCHs, mainly alpha- and beta-HCH, have been found more than 2 m below ground level.
Pollution of ground water was also detected, but this was restricted to the vicinity of the production areas.
In milk and milk products samples the average level was 0. Table 2 gives the mean alpha-HCH levels in a large number of samples of various food items from the Federal Republic of Germany reported by Hildebrandt et al.
In a total-diet study in the United Kingdom, 24 samples of each food group were analysed for alpha-HCH. The following concentrations mean and range were found: Imported meat products were also analysed during the periodand concentrations of up to 0. Imported retail cereal products collected in contained alpha-HCH levels of up to 0.
Various types of pulses were analysed during the periodand 31 out of samples contained alpha-HCH residues at levels of up to 0. Processed pork and poultry, sampled during the periodcontained alpha-HCH at levels of up to 3. Of other processed meat products, samples were negative. Retail milk and dairy products were analysed during the periodand of the samples contained alpha-HCH residues at a mean concentration of 0.
Samples of eel muscle eels from 62 sites were analysed during the periodand mean concentrations were 0. The mean residue level of alpha-HCH in milk samples collected during spring from bulk transporters representing 16 counties, municipalities, and districts of Ontario was 5.
In a study by Gaggi et al. The leaves were from ten different species of trees and two different lichen species were involved. The same authors reported that the levels of alpha-HCH in various plant species collected in 14 countries were 0. Alpha-HCH concentrations in carp of up to 0. Cowan studied the extent of pollution of Scottish coastal waters by HCHs using Mytilus edulis as biological indicator.
The fish and shellfish sampling programme carried out by the United Kingdom Ministry of Agriculture, Fisheries, and Food between was directed mainly to areas around the coasts of England and Wales.
The mean alpha-HCH concentration in the muscle of flounders collected off the North Sea coast of Germany in was 2.
Bream collected from different locations in the River Elbe between Schnackenburg and the North Sea contained 0. Freshwater fish from different rivers in the Federal Republic of Germany were analysed during the periodand in the first years the alpha-HCH levels were mainly between 0. However, a clear decrease then took place and most of the samples were below 0. Flounders and herrings caught in the North Sea contained 0.
Alpha- and beta-hexachlorocyclohexanes (EHC , )
The mean levels and range in muscle, liver, fat, brain, and kidneys in total 91 samples were 0. Residues of alpha-HCH were found in all of the 37 specimens of long-tailed duck at mean concentrations on a fat basis of 3. These results are in agreement with those of Benson et al.
Adipose tissue contained 0. The study covered 20 to 24 food groups, and the number of total-diet samples examined varied from 22 to 25 samples. The calculated mean alpha-HCH residue levels in the total diet for the periods,, and were 0.
Ch alpha and beta forms
The samples, purchased from retail outlets, were representative of the diets of adults in 20 cities, and consisted of about individual food items. The daily intake of alpha-HCH in, and was 0. In a similar way, samples were collected in 10 cities in consisting of about 50 items of infant food and items of toddler food. The daily intake of alpha-HCH in, and was, respectively, 0. Total-diet studies conducted in the USA by the FDA before were based on a "composite sample approach" regardless of the diet involved.
Later on they were based on dietary survey information and allowed the "total diet" of the population to be represented by a relatively small number of food items for a greater number of age-sex groups. The daily intakes of alpha-HCH during for the age groups months, 2 years, year-old females, year-old males, year-old females, year-old males, year-old females, and year-old males were 7.
In a total-diet study in the Netherlands inthe average concentration of alpha-HCH in samples was 0. The highest level was 0. The median concentration for both groups was below the detection limit 0. The mean concentration was 0. InReiner et al. In 57 of the samples, alpha-HCH was found at a mean concentration of 3.
Similar values were found in other parts of the country in Krauthacker et al. The median concentration of alpha-HCH in whole blood of people in the Federal Republic of Germany was reported to be 0. In a study by Niessen et al. The average concentration of alpha-HCH was 0. The average concentration was highest 0. The mean alpha-HCH concentrations samples ranged from 0. Insamples of adipose tissue were collected in eight regions of Japan and the mean level of alpha-HCH was 0.
Twenty-nine samples of adipose tissue were taken at necropsy and 24 at surgery in the Poznan district of Poland and compared with samples from residents of the Warsaw area. In Poznan the mean concentration of alpha-HCH was 0. In a Swedish study, the levels of alpha-HCH in breast milk were found to be related to the dietary habit.
Levels in lacto-vegetarians were lower than those in women eating a mixed diet, and these were lower than those found in mothers using a mixed diet that regularly included fatty fish from the Baltic Noren, Alpha-HCH concentrations of up to 0.
Residues of alpha-HCH in breast milk during the periods, and in the Federal Republic of Germany were reported to be 0. In the Federal Republic of Germany, more than samples of breast milk were analysed from These studies were carried out by 20 authors, and the results were summarized by Hildebrandt et al. The mean concentrations of alpha-HCH ranged from 0. In one case a mean concentration of 0.
During the period investigated, a slow decrease in the mean concentration of alpha-HCH was observed. The average concentration in breast milk in the same country samples in was 0.
Insamples of breast milk were analysed and the average level was 0. Tuinstra analysed 36 individual samples of breast milk, collected infrom young mothers years of age living in the Netherlands. A median alpha-HCH concentration of 0.
The alpha-HCH levels were significantly lower in the autumn than in the spring mean concentrations of 0. In a study in rats with 36Cl-labelled alpha-HCH, a low excretion rate was found.“Relationships” Are Beta, Procreation Is Alpha
During continued dosing alpha-HCH was observed to stimulate its own degradation Noack et al. The decrease in rat liver alpha-HCH levels after an initial increase, observed by Eichler et al. In the faeces and urine, 3. With an average blood concentration of 1. Similarly, Macholz et al. In the brain, alpha-HCH is stored preferentially in the white matter Stein et al. The biotransformation of alpha-HCH in rats involves dechlorination Kraus, The major urinary metabolite in rats is 2,4,6-trichlorophenol, a compound reported by IARC to be carcinogenic for animals Portig et al.
Other metabolites that have been identified are 1,2,4-trichlorophenol, 2,3,4-trichlorophenol, 2,4,5-trichlorophenol, 2,3,4,5- tetrachlorophenol, and 2,3,4,6-tetrachlorophenol Noack et al. In addition, chlorothiophenols not specified have been detected, and 1,3,4,5,6-pentachlorocyclohexene has been identified in the kidneys of rats Macholz et al.
The cerebella of the animals were analysed and the following metabolites were found: Alpha-HCH was present at This study showed that the HCH isomers are cleared from the brain via different metabolic pathways.
Isomerization of alpha-HCH to lindane did not occur after repeated dosage Eichler et al. Biotransformation to one or more of the other HCH isomers was not detected Szokolay et al. The pentachlorocyclohexenes, tetrachlorophenol, hexachlorobenzene, and pentachlorophenol were also identified in the blood.
It is important to note that the linear form of glucose makes up less than 0. The rest is one of two cyclic forms of glucose that are formed when the hydroxyl group on carbon 5 C5 bonds to the aldehyde carbon 1 C1. Cyclic forms of glucose.
From left to right: The open-chain form is limited to about 0. The terms "glucose" and "D-glucose" are generally used for these cyclic forms as well. The ring arises from the open-chain form by an intramolecular nucleophilic addition reaction between the aldehyde group at C-1 and either the C-4 or C-5 hydroxyl group, forming a hemiacetal linkage, -C OH H-O.
The reaction between C-1 and C-5 yields a six-membered heterocyclic system called a pyranose, which is a monosaccharide sugar hence "—ose" containing a derivatised pyran skeleton.
The much rarer reaction between C-1 and C-4 yields a five-membered furanose ring, named after the cyclic ether furan. The ring-closing reaction makes carbon C-1 chiraltoo, since its four bonds lead to -H, to -OH, to carbon C-2, and to the ring oxygen.
Therefore, the open-chain isomer D-glucose gives rise to four distinct cyclic isomers: These five structures exist in equilibrium and interconvert, and the interconversion is much more rapid with acid catalysis. The rings are not planar, but are twisted in three dimensions. Similarly, the glucofuranose ring may assume several shapes, analogous to the "envelope" conformations of cyclopentane. In the solid state, only the glucopyranose forms are observed, forming colorless crystalline solids that are highly soluble in water and acetic acid but poorly soluble in methanol and ethanol.
Rotational isomers[ edit ] Each glucose isomer is subject to rotational isomerism. Mutarotation[ edit ] Mutarotation: Mutarotation consists of a temporary reversal of the ring-forming reaction, resulting in the open-chain form, followed by a reforming of the ring.
Thus, though the open-chain form is barely detectable in solution, it is an essential component of the equilibrium. The open-chain form is thermodynamically unstableand it spontaneously isomerizes to the cyclic forms.
Although the ring closure reaction could in theory create four- or three-atom rings, these would be highly strained, and are not observed in practice. In solutions at room temperaturethe four cyclic isomers interconvert over a time scale of hours, in a process called mutarotation. The strength of the effect is different for each of the five tautomers. Note that the D - prefix does not refer directly to the optical properties of the compound. It indicates that the C-5 chiral center has the same handedness as that of D -glyceraldehyde which was so labeled because it is dextrorotatory.