Why is ethanol corrosive

Molecules, school book

44 3 ORGANIC OXYGEN COMPOUNDS Technical ethanol is sold in the form of alcohol (alcohol concentration approx. 90%). In order to prevent the evasion of the alcohol tax by selling the alcohol intended for technical purposes as pleasure alcohol, ethanol is made inedible by adding petrol and some other substances ("denatured alcohol"). The technical importance of ethanol is steadily declining as it is being replaced by methanol in many cases. A number of the ethanol by-products, such as ethanal (acetaldehyde), can be produced more cheaply from methanol. Ethanol is used as a solvent and in the production of ethyl esters. Ethanol is toxic in high concentrations. It is also used as a preservative. In the form of alcoholic beverages, it has a stimulating effect in smaller quantities; in larger quantities, acute symptoms of poisoning can occur (headache, nausea). High doses can lead to unconsciousness and death (jumping over the "barrier to unconsciousness" by quickly drinking high-percentage beverages). Regularly consumed alcohol can lead to psychological dependence and severe physical damage (e.g. cirrhosis of the liver). Due to the stimulating effect of alcohol, people who are under the influence of alcohol tend to overestimate themselves. However, even with small amounts of alcohol, the ability to react and the ability to see (eg limited viewing angle) are severely impaired. In Austria, the legal limit for road users is a blood alcohol content of less than 0.5 ‰. This limit is often viewed as too high, since even at this value an impairment of driving ability occurs. Ethanol has a high nutritional value (approx. 30 kJ / g). Alcoholics mostly cover a large part of their energy needs with alcohol. Deficiencies in vitamins and other important food components increase the harmful effects of ethanol. Ethanol expands the skin vessels ("drunkards nose"). This leads to increased heat dissipation and a drop in body temperature. Other short-chain alcohols: They are solvents or extractants or ester components and are often technically more important than ethanol. (Fig. 44.1) During alcoholic fermentation they arise as decomposition products of the yeast protein (“fusel oils”) and are extremely harmful to health at higher concentrations. Allyl alcohol (propenol) (Fig. 44.2) Allyl alcohol is one of the most important unsaturated alcohols. It is obtained either from glycerol or from propene. It is a breath poison and has a very corrosive effect. The double bond makes allyl alcohol reactive. It serves as the starting material for a large number of products such as components for the manufacture of special plastics. Fatty alcohols (Fig. 44.3) Fatty alcohol is a collective name for long-chain unbranched primary alcohols. In the narrower sense, only alcohols with an even number of carbon atoms between 8 and 22 are fatty alcohols. Longer chains are called wax alcohols. Detergent substances (surfactants) are produced from fatty alcohols. Cholesterol (Cholesterol) (Fig. 44.4) Cholesterol is found in nerve cells, the brain and the spinal cord. Gallstones can consist entirely of cholesterol. It is produced in the liver (up to 2 g / day) and also taken up with food (0.1–1.4 g / day depending on the fat content of the food). It is used in the organism to synthesize hormones (sex hormones), but is also involved in building up nerve cells and has an important protective function for the skin. In the blood, cholesterol is bound to proteins (lipoproteins). In a simplified way, a distinction is made between those with high density (HDL = high density lipoprotein) and those with low density (LDL). High concentrations of LDL in particular can lead to cholesterol deposits on the arterial walls (arteriosclerosis). This is considered to be a major cause of heart attack and stroke. You should therefore have the “cholesterol level” in your blood checked regularly, and if the values ​​are high, you should eat low-fat and exercise. Fig. 44.1: Overview of the short-chain alcohols C 3 -alkanols: 2 isomers, water-miscible. Use: solvents, ester components, acetone production (propan-2-ol). C 4 alkanols: 4 structural isomers, poorly soluble in water. Use: solvents, ester components (plasticizers), brake fluid. C 5 alkanols: 8 structural isomers, poorly soluble in water. Use: solvents, ester components, pharmaceutical intermediates. C 5 alkanols are also called “amyl alcohols”. They arise as by-products of the fermentation mainly of starch-containing raw materials (amylum = starch). Fig. 44.4: Formula and molecular model of cholesterol Fig. 44.2: Formula and molecular model of allyl alcohol C C H C H H O H H H Fig. 44.3: Formula of decan-1-ol, a fatty alcohol CH 2 O H H O For testing purposes only - property of the publisher öbv

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