Section 1.4 ORGANIC HALIDES

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Section 1.4 ORGANIC HALIDES

Organic halides: A compound of carbon and hydrogen in which one or more hydrogen atoms have been replaced by halogen atoms.

Functional group: R – X

Used in: 

  • Freons (chlorofluorocarbons, CFCs) used in refrigerators and air-conditioners
  • Teflon (polytetrafluoroethene), the nonstick coating used in cookware and labware
  • The insecticide DDT (dichlorodiphenyltrichloroethane) and the PCBs (polychlorinated biphenyls) used in electrical transformers

Naming Organic Halides: Consider the halogen atom as an attachment on the parent hydrocarbon. The halogen name is shortened to fluoro-, chloro-, bromo-, or iodo.

Preparation:

  • alkenes and alkynes  organic halides

addition reactions with halogens or hydrogen halides

  • alkanes and aromatics  organic halides

substitution reactions with halogens or hydrogen halides

Pathway to other groups: 

  • alkyl halides  alkenes

elimination reactions, removing hydrogen and halide ions

Properties of Organic Halides: The halogen atom on a hydrocarbon chain/ring makes the molecule more polar as the halogens are more electronegative than C and H atoms. Therefore, halogen bonds are more polar than C – H bonds. The increased polarity of alkyl halides increases the strength of the intermolecular forces. Thus alkyl halides have higher boiling points than the corresponding hydrocarbons. The increased polarity makes them more soluble in polar solvents than hydrocarbons of similar size because “like dissolves like”.

Section 1.5 ALCOHOLS and ETHERS

Alcohol: An organic compound characterized by the presence of a hydroxyl functional group; R – OH

Preparation: 

  • alkenes  alcohols

addition reaction with water: hydration

Pathways to other groups: 

  • alcohols  alkenes

elimination reaction: dehydration

  • alcohols  aldehydes  carboxylic acids

controlled oxidation reaction

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1o, 2o, and 3o Alcohols

        Alcohols are classified according to the type of carbon to which the –OH group is attached. Since C atoms form four bonds, the C atom bearing the –OH group can be attached to a further 1, 2, or 3 alkyl groups, the resulting alcohols classified as primary, secondary, and tertiary alcohols (1o, 2o, and 3o).

Polyalcohols

        Alcohols that contain more than one hydroxyl group are called polyalcohols; the suffixes –diol and –triol are added to the entire alkane name to indicate two and three –OH groups, respectively. The abundance of –OH groups makes it a good ...

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