Xenobiotics are substances which the body doesn't contain but which can effect it. There are three types:
Ethanol is an alcohol which is a source of energy, affects our behaviour and in excess, can cause liver damage and even death. Alcoholic drinks help people to relax by depressing the activity of the central nervous system. It slows our reaction times and impairs our judgement.
Blood alcohol concentration (BAC) is closely related to the extent of the effects of alcoholic drinks. Ethanol is sufficiently volatile to pass from the blood to the air in the lungs. An equilibrium is set up:
Kc has a fixed value at a particular temperature. Therefore a measurement of the ethanol concentration in the breath gives an indication of the BAC. An early breathalyser is based on the reaction between potassium dichromate (VI) crystals which are orange. They turn green when they oxidise ethanol to ethanal and ethanoic acid.
Roadside breath tests are not particularly reliable. A more accurate technique is to use gas-liquid chromatography on either a blood sample or a urine sample. A more recent technique is to use infra-red spectroscopy on a breath sample.
Alcohols contain the hydroxyl group -OH. Alcohols are soluble in water because they are able to form H-bonds with water. The solubility decreases as you go down the homologous series.
There are three types of alcohols:
The reactions of alcohols are summarised below:
|2C2H5OH + 2Na||2C2H5ONa||+ H2|
|C2H5OH + CH3CO2H||CH3CO2C2H5||+ H2O|
|C2H5OH + HBr||C2H5Br||+ H2O|
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