• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Find out how halogens are used in the manufacture of herbicides and polymers and environmental problems associated

Extracts from this document...

Introduction

Find out how halogens are used in the manufacture of herbicides and polymers and environmental problems associated. Organohalogen compounds are organic compounds that contain at least one halogen (fluorine [F], chlorine [Cl], bromine [Br], or iodine [I]) bonded to carbon. They are subdivided into alkyl, vinylic, aryl, and acyl halides. In alkyl halides all four bonds to the carbon that bears the halogen are single bonds; in vinylic halides the carbon that bears the halogen is doubly bonded to another carbon; in aryl halides the halogen-bearing carbon is part of an aromatic ring; and in acyl halides (also called acid halides) the halogen-bearing carbon is doubly bonded to oxygen. Organohalogen compounds differ widely in chemical reactivity, depending on the halogen and the class to which they belong, and they may even differ within a class. A halogen substituent is considered a functional group, and the transformations of organohalogen compounds rank among the most important in organic chemistry. Many organohalogen compounds, especially organochlorine compounds, are important industrial chemicals; they are used as solvents and pesticides and as intermediates in the preparation of dyes, drugs, and synthetic polymers. ...read more.

Middle

are sometimes applied by the jar method, whereby the tops of weeds are bent over and immersed in jars of poisonous solution. The herbicide is drawn into the rest of the plant and into connecting plants, gradually killing the entire system. Wild morning glory, poison oak, and camel thorn are sometimes treated in this manner. Chlorinated benzene and certain aromatic solvents are used to control aquatic weeds by adding them directly to the watery medium. Herbicides are chemicals used to kill plants. Their potential to produce toxicity in humans is rather low. High doses of 2,4-D, however, can produce muscular and neurological symptoms (Table 1). The systemic toxicity of 2,4,5-T is lower than that of 2,4-D, but 2,4,5-T is more irritating.During the Vietnam War, Agent Orange, a mixture of 2,4-D and 2,4,5-T, was used as a defoliant. The 2,4,5-T used in the Agent Orange was contaminated with tetrachlorodibenzodioxin (TCDD), or dioxin. Although TCDD is extremely toxic to some animals, it is less so to others, but it does cause birth defects and cancer in laboratory animals. ...read more.

Conclusion

High DDT levels in birds were associated with fragile eggshells and reproductive abnormalities. Potential harm to wildlife and humans, along with the fact that many insects had become resistant to DDT, prompted the United States Environmental Protection Agency (EPA) to impose an almost complete ban on its use in 1972.A second chlorine-containing aromatic compound that is widespread in the environment is 2,3,7,8-tetrachlorodibenzo-p-dioxin (known simply as dioxin).Dioxin is formed in small amounts as a by-product in the synthesis of the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), in chlorine-based bleaching processes during paper production, and whenever organic material burns in the presence of a source of chloride ion Cl-, as in forest fires, for example. It is a very stable compound and gradually accumulates in the environment. Because dioxin is exceedingly toxic, carcinogenic, and teratogenic to test animals, regulations designed to limit further environmental contamination have been implemented.A group of aryl halides called polychlorinated biphenyls (PCBs) were formerly prepared on a large scale for use as heat-transfer mediums and insulating materials in transformers and other electrical equipment. Many of the problems associated with DDT and dioxin as environmental pollutants apply to PCBs as well, and PCB production was banned by the EPA in 1979. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Living Things in their Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Living Things in their Environment essays

  1. What Factors are responsible for the success of Insects?

    compound eyes), small size, high reproductive rate and the exoskeleton are common to all and are the reasons behind the success of the phylum as a whole. Comparison between the insects, crustaceans and arachnids is useful and can be revealing.

  2. Fungal Pathogens in Humans.

    In pregnant women, the likelihood of vaginal candidiasis is high since there is an increase in glycogen levels in mucosal tissues, which stimulates overgrowth of Candida. This infection may be passed as thrush to her baby following birth, before the natural flora of protective bacteria is established (Kendrick, 2000).

  1. Branded Bleach is more effective at killing E. coli than Non branded bleach - ...

    will mean more bacteria may be present in one Petri dish than the other and increase the chance of contamination. Using a thermostatically controlled incubator the temperature can be very accurately monitored. 5) Volume of E. coli This will ensure that the same number of bacteria are used in each Petri dish Using a very accurate micropipette.

  2. Evolution, Natural selection and Darwinism

    The best example can be seen from he Galapagos finches as their bills are specialized to eat different food of their own island. <Ref.1 - p448, p452-453 & Ref.4 - p207-208> Sympatric speciation In sympatric speciation, intrinsic factors, such as chromosomal changes (in plants)

  1. Science Chemistry Casestudy

    Ensures that consumers have access to affordable food that is also safer and more nutritious. - Produces larger crops - Helps farmers increase crop productivity and quality - Helps remove the hardship of hand weeding - Helps safeguard public health by controlling or eliminating pests that cause disease and property damage.

  2. Early Humans?

    ramidus maybe have existed shortly after the ape-hominin split. The post-cranial remains, which consist of a right humerus, and a left humerus, ulna, and radius, display a mosaic of primitive and derived characteristics, which suggests the animal still spent time in trees (White et.

  1. Grizzly Bears

    Their first meal after their winter hibernation would probably be a carcass of a moose or caribou that didn't survive the winter. Grizzlies have to eat a lot in order to survive the winter when they hibernate. Near the sea, grizzlies may find a beached whale or a dead sea lion or walrus.

  2. An Investigation to find the Effect of Distance from the Sea on the Number ...

    The high inter-tidal zone - This zone is only covered with water only when it is high tides. This zone experiences wave motion (wave action), therefore, species living in this zone must have special adaptations as they must attach themselves securely to the rocks.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work