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Chlorinated pesticides

Hydrocarbons combined with chlorine are among the most effective insecticides known. Most familiar of this group is DDT (dichlorodiphenyl-trichloroethane). DDT is termed a "hard" insecticide because it can exist in soil and water systems for months or even years. Other hard insecticides include Aldrin, Dieldrin, and Lindane. Their use is severely re-


stricted. Although they successfully eradicate disease-transmitting insects and crop preda­tors, they are also hazardous to humans. Many herbicides are also halogenated hydrocar­bons. The most widely used is a wheat herbi­cide.


Recordsare made largely of PVC, with the addition of plasticizers to make the rec­ords flexible. PVC is one of the best-known and most widely used of the vinyl polymers. In its rigid, un-plasticized form it is used for pipes and guttering. In its flexible, plasticized form, it is used for pliable sheet­ing, electrical insulation, nonflammable upholstery coverings, floor tiles, and clothing.



Alcohol(ethanol) has long been made by fermentation. During this process, en­zymes from yeast cells (shown highly magnified, right) bring about the breakdown of starch or sugar into alcohol and car­bon dioxide. The process is still the basis of the brewing industry for beer and lager and for the production of spirits such as whiskey (far right).


       
   
 
 


-CH3
-CH2 1
1 -CH
O -c-
The boiling pointsof pri­mary alcohols (red line) are higher than the boiling points of their isomeric counterparts. Secondary isomers lie along the purple line. Tertiary isomers he along the orange line. These secondary and tertiary iso­mers have the same molec­ular weight and lie on the same vertical line on the di­agram as their primary alco­hols. (*C) *CF)

1=180,

& 160


•O -OH


;'m

Propanol 2-butanol Jr 5


 
Ethanol • O* ^r 2-propanol
170 Methanol



Alcohols

Alcohols are some of the most common and widely used chemicals. Methanol (methyl alco­hol) is the simplest. It has been used for many years as a solvent in dissolving other sub­stances and as a fuel. Another well-known al­cohol is ethanol, or ethyl alcohol. It has been used for thousands of years as an intoxicating ingredient in alcoholic beverages such as wine, spirits, mead, and ale. Ethanol is also im­portant industrially as a solvent and as a reac­tion medium, which acts on other substances to form further substances.


Date: 2015-12-11; view: 732


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