Halo Groups

 Halo Groups

What do they call the followers of the Organic Chemistry god? Halo Groups!

Halo Groups are more commonly known as Alkyl Halides

Uses
Alkyl Halides can be used as


 * refrigerants,


 * propellants for aerosols


 * for generating foamed plastics like expanded polystyrene or polyurethane foam


 * as solvents for dry cleaning and for general degreasing purposes

The naming of Alkyl Halides (halogens: F, Cl, Br, I attached to alkanes) is straightforward.

Rules and Properties
RULE: Name alkyl halides in the same manner as alkyl groups.
 * Attached F, Cl, Br, and I atoms are called ‘fluro’, ‘chloro’, ‘bromo’, and ‘iodo’ groups. (The general term for an attached halogen atom is a ‘halo’ group.)
 * Use a number to indicate the position of attachment on the hydrocarbon chain.
 * If more than one of the same kind of halogen is present, uses the prefixes di, tri, etc.
 * If a compound contains both alkyl groups and halo groups, list the attached groups in alphabetical order. Number from the end which gives the lowest set of numbers.

Properties of Alkyl Halides

 * Alkyl halides are usually insoluble in water, like alkanes
 * Compounds with many fluorine atoms tend to be unreactive (inert). ‘Teflon’ is a hightail fluorinated hydrocarbon, and is inert to almost all chemical attack
 * Chloro and broom compounds are susceptible to chemical attack, but require drastic conditions. Iodo compounds are more reactive.

Try it yourself!
NOTE: Unlike alkyl groups attached to straight-chain carbon, halo groups can be placed at the 1-postion

EXAMPLES:

CH3-Cl = chloromethane

CCl3-CF3 = 1,1,1-trichloro-2,2,2-trifluoroethane





EXCERCISES: Draw the following
 * 1) trichloromethane (chloroform)
 * 1,2-dichloroethane
 * 1,1,1-trifluoro-2-methylpentane

Name the following

4) CH3-CH2-Cl

5)  CH2F-CHCL2

6)



ANSWERS:

1) CHCL3

2) ClCH2CH2Cl