Alcohol

From ArticleWorld

Most people don't realize that their bodies contain scores of types of alcohols even if they've never taken a drink. To an organic chemist, an alcohol is any compound with a hydroxyl group attached to a saturated carbon atom. A "saturated" carbon atom is one which is attached to four other atoms; a hydroxyl group is the organic chemist's name for an "almost molecule" consisting of one oxygen and one hydrogen atom.

By this chemical definition, cholesterol is an alcohol. But what concerns us here is ethyl alcohol, also known as ethanol. It takes its name because a hydroxyl group is added to a saturated, two-carbon configuration which organic chemists call an ethyl group. Ethanol is inescapable because all it takes to get fermentation started is sugar and yeast -- both of which are ubiquitous in our environment and food supply. Take a molecule of glucose; add yeast and very quickly you get two molecules each of alcohol and carbon dioxide. Laboratory samplings of commonly consumed fruit juices and sugar-based soft drinks purchased from a supermarket (and tested right from the carton the day they were put on the store shelf) all showed measurable amounts of ethanol, up to 0.1 percent. The amount of ethanol in some of the samples doubled or tripled after only three days in the refrigerator.

In chemistry, an alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom, which in turn is bound to other hydrogen and/or carbon atoms. The general formula for a simple acyclic alcohol is CnH2n+1OH. In general usage, alcohol refers almost always to ethanol, also known as grain alcohol, a colorless, volatile liquid, formed by the fermentation of sugars. It also often refers to any beverage that contains ethanol (see alcoholic beverage). This sense underlies the term alcoholism (addiction to alcohol). As a drug, ethanol is known to have a depressing effect that decreases the responses of the central nervous system. The word alcohol dates to the 16th century when it was used to refer to any chemical substance arrived at by sublimation. This derived from the Medieval Latin alcohol ("powdered ore of antimony"), originating from Arabic al-kuḥūl (الكحول). Structure

The functional group of an alcohol is a hydroxyl group bonded to an sp³ hybridized carbon. It can therefore be regarded as a derivative of water, with an alkyl group replacing one of the hydrogen’s. If an aryl group is present rather than an alkyl, the compound is generally called a phenol rather than an alcohol. Also, if the hydroxyl group is bonded to one of the sp² hybridized carbons of an Ankeny group, the compound is referred to as an enol. Primary, secondary, and tertiary alcohols

There are three major subsets of alcohols- 'primary' (1°), 'secondary' (2°) and 'tertiary' (3°), based upon the number of carbons the C-OH carbon (shown in red) is bonded to. Methanol is the simplest 'primary' alcohol. The simplest secondary alcohol is isopropanol (propan-2-ol), and a simple tertiary alcohol is tert-butanol (2-methylpropan-2-ol).

Methanol & ethanol

The simplest and most commonly used alcohols are methanol and ethanol (common names methyl alcohol and ethyl alcohol, respectively), which have the structures shown above. Methanol was formerly obtained by the distillation of wood, and was called "wood alcohol". It is now a cheap commodity chemical produced by the high pressure reaction of carbon monoxide with hydrogen. In common usage, "alcohol" often refers simply to ethanol or "grain alcohol". Methylated spirits ("Meths"), also called "surgical spirits", is a form of ethanol rendered undrinkable by the addition of methanol. Aside from its major use in alcoholic beverages, ethanol is also used (though highly controlled) as an industrial solvent and raw material.

Uses

Ethanol and methanol can be made to burn more cleanly than gasoline or diesel. Because of its low toxicity and ability to dissolve non-polar substances, ethanol is often used as a solvent in medical drugs, perfumes, and vegetable essences such as vanilla. In organic synthesis, alcohols frequently serve as versatile intermediates. Ethanol is also commonly used in beverages after fermentation to promote flavor or induce a euphoric intoxication commonly known as "drunkenness" or "being drunk". The use of ethanol for this purpose is illegal in some countries, mainly Islamic.

Alcoholism has become one of the most common drug addictions (perhaps behind caffeine) in the world. The physiological dependency caused by alcoholism means that the user experiences physical withdrawal (in the form of a headache known as a "hangover," extremely high anxiety known as "the shakes," and restlessness or trouble sleeping) upon cessation or decrease of use. For the full article on this topic see effects of alcohol on the body.

Effects of alcohol on the body

The amount and circumstances of consumption play a large part in determining the extent of intoxication, e.g. consuming alcohol after a heavy meal is less likely to produce visible signs of intoxication than consumption on an empty stomach. Hydration also plays a role, especially in determining the extent of hangovers. Initially, alcohol generally produces feelings of relaxation and cheerfulness, but further consumption can lead to blurred vision and coordination problems. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every tissue of the body. After excessive drinking, unconsciousness can occur and extreme levels of consumption can lead to alcohol poisoning and death.

Alcoholism, addiction to alcohol, is a major public health problem. Alcoholics develop a number of health problems, with cirrhosis of the liver among the most significant. Unlike withdrawal from some other drugs/intoxicants such as the opioids, withdrawal from heavy alcohol consumption can produce delirium tremens that can be fatal. Excessive alcohol consumption during pregnancy carries a heavy risk of permanent mental and physical defects in the child, known as fetal alcohol syndrome.

Alcohol is not an ordinary commodity. While it carries connotations of pleasure and sociability in the minds of many, harmful consequences of its use are diverse and widespread. From a global perspective, in order to reduce the harm caused by alcohol, policies need to take into account specific situations in different societies. Average volumes consumed and patterns of drinking are two dimensions of alcohol consumption that need to be considered in efforts to reduce the burden of alcohol-related problems. Avoiding the combination of drinking and driving is an example of measures that can reduce the health burden of alcohol.

Worldwide, alcohol takes an enormous toll on lives and communities, especially in developing countries and its contribution to the overall burden of disease is expected to increase in the future. National monitoring systems need to be developed to keep track of alcohol consumption and its consequences, and to raise awareness amongst the public and policy-makers. It is up to both governments and concerned citizens to encourage debate and formulate effective public health policies that minimize the harm caused by alcohol.