Alcohols are organic compounds containing the hydroxyl group (-OH). They are named as hydrocarbons* but with the ending "-OL", and indicating with a locator number, the lowest possible (naming it from the closest carbon to the -OH), the position of the alcoholic group. Alcohols can be classified in primary, secondary and tertiary, according to the amount of carbons bonded to the hydroxyl.
Primary Alcohol: Bonded to only one other carbon atom.
Secondary Alcohol: The hydroxyl group is on the secondary carbon atom, which is bonded to two other carbon atoms.
Tertiary Alcohol: It has the hydroxyl group on a tertiary carbon atom, which is bonded to three other carbon.
CH3 -OH
It is a polar organic solvent and is widely used as an industrial and marine solvent and paint remover. It is also used in photocopying fluid, shellacs, and windshield-washing fluids. Although toxicity primarily occurs from ingestion, it can also occur from prolonged inhalation or skin absorption. This alcohol is more toxic than ethanol and may cause blindness or death if large amounts are inhaled or ingested. Methanol is rapidly absorbed from the gastric mucosa, and achieves a maximal concentration 30-90 minutes after ingestion. Methanol is primarily metabolized in the liver via alcohol dehydrogenase into formaldehyde. Formaldehyde is subsequently metabolized via aldehyde dehydrogenase into formic acid, which ultimately is metabolized to folic acid, folinic acid, carbon dioxide, and water. A small portion is excreted unchanged by the lungs.
Formic acid is responsible for the majority of the toxicity associated with methanol.
Ethanol
CH3 -CH2 -OH
Ethyl alcohol is a low molecular weight hydrocarbon that is derived from the fermentation of sugars and cereals, such as corn (maize), wheat, rye, and barley. It is widely available both as a beverage and as an ingredient in food extracts, cough and cold medications, and mouthwashes.
Ethanol is rapidly absorbed across both the gastric mucosa and the small intestines, reaching a peak concentration 20-60 minutes after ingestion. Once absorbed, it is converted to acetaldehyde. This conversion involves three discrete enzymes: the microsomal cytochrome, isoenzyme, the cytosol-based enzyme alcohol dehydrogenase (ADH), and the peroxisome catalase system. Acetaldehyde is then converted to acetate, which is converted to acetyl CoA, and ultimately carbon dioxide and water.
Genetic polymorphisms coding for alcohol dehydrogenase, the amount of alcohol consumed, and the rate at which ethanol is consumed all affect the speed of metabolism. As a general rule, ethanol is metabolized at a rate of 20-25 mg/dL in the nonalcoholic but at an increased rate in chronic alcoholics.
Isopropanol
CH3 -CH-OH-CH3
Isopropyl alcohol is a low molecular weight hydrocarbon. It is commonly found as both a solvent as well as a disinfectant. It can be found in many mouthwashes, skin lotions, rubbing alcohol, and hand sanitizers. Because of its widespread availability, lack of purchasing restrictions, and profound intoxicating properties, it is commonly used as an ethanol substitute.
Isopropanol is rapidly absorbed across the gastric mucosa and reaches a peak concentration approximately 30-120 minutes after ingestion. Isopropanol is primarily metabolized via alcohol dehydrogenase to acetone. A small portion of isopropanol is excreted unchanged in the urine. The peak concentration of acetone is not present until approximately 4 hours after ingestion. The acetone produces CNS depressant effects and a fruity odor on the breath.
Ethylene glycol
The glycol is made from ethylene. Its systematic name is ethane-1,2-diol. Ethylene glycol is commonly used as automotive antifreeze and as an ingredient in hydraulic fluids, printing inks, and paint solvents. It is also used as a reagent in making polyesters, explosives, alkyd resins, and synthetic waxes.
Glycerol
Glycerol is a sweet syrupy substance with three alcohol hydroxyl groups. Its systematic name is propane-1,2,3-triol. Glycerol was first obtained as a byproduct of soap manufacture, through the saponification (hydrolysis in base) of fats. It can also be obtained by fermentation from molasses and sugar.
A large amount of glycerol is still used for making nitroglycerin, which is the primary explosive in dynamite and blasting gelatin. Nitroglycerin is also used as a coronary vasodilator (a drug that relaxes and expands blood vessels) for symptomatic relief of chest pain caused by poor circulation to the heart. Glycerol is also used as a solvent, moisturizing agent, plasticizer, antifreeze, and water-soluble lubricant. It is found in a wide variety of products, including foods, soaps, cosmetics, printing inks, hydraulic fluids, and pharmaceuticals.
Acute intoxication with any of the alcohols can result in respiratory depression, aspiration, hypotension, and cardiovascular collapse.
Preparation of alcohol
Alcohol or an alcoholic beverage is produced by a process wherein a mash of cereal grains and liquefying enzymes is cooked at a temperature of from 75° C to 85° C which is lower than the temperature of maximum viscosity for the mash and which is higher than the sterilization temperature of undesirable microorganisms in the mash which grow during fermentation with yeast. After cooking, the mash is cooled, saccharifying enzymes are added, the resultant mash is fermented with yeast to produce alcohol and the alcohol is distilled.
In the world there is a great variety of alcoholic drinks all with a different alcoholic graduation. This page has a table showing the graduation of some of the world's drinks.
Breathalyzer
The Breathalyzer device contains:
- A system to sample the breath of the suspect
- Two glass vials containing the chemical reaction mixture
- A system of photocells connected to a meter to measure the color change associated with the chemical reaction
To measure alcohol, a suspect breathes into the device. The breath sample is bubbled in one vial through a mixture of sulfuric acid, potassium dichromate, silver nitrate and water. The principle of the measurement is based on the following chemical reaction:
In this reaction:
The sulfuric acid removes the alcohol from the air into a liquid solution. The alcohol reacta with potassium dichromate to produce: chromium sulfate, potassium sulfate, acetic acid and water.
The silver nitrate is a catalyst, a substance that makes a reaction go faster without participating in it. The sulfuric acid, in addition to removing the alcohol from the air, also might provide the acidic condition needed for this reaction.
During this reaction, the reddish-orange dichromate ion changes color to the green chromium ion when it reacts with the alcohol; the degree of the color change is directly related to the level of alcohol in the expelled air. To determine the amount of alcohol in that air, the reacted mixture is compared to a vial of unreacted mixture in the photocell system, what ich produces an electric current that causes the needle in the meter to move from its resting place. The operator then rotates a knob to bring the needle back to the resting place and reads the level of alcohol from the knob.
