Organic Halides (Haloalkanes) (Alkyl Halides) Functional Group #1

Structure R-X where R = alkyl group and X = halide (F, Cl, Br, I)      Cl                    |            CH=C-CH2-CH3 |                     Cl                    1,2-dichloro-1-butene bromoethane

Prefixes for the first four members of the halogen family Nomenclature Fluorine Fluoro- Chlorine Chloro- Bromine Bromo- Iodine Iodo- Prefixes for halides are inserted into the name of the structure in the exact same fashion as any alkyl group. Remember to write them in alphabetical order Prefixes for the first four members of the halogen family

Properties The presence of a halide makes the molecule more polar. Since water is also polar and “like dissolves like”, alkyl halides are soluble in water. The more halides connected to the parent chain, the more polar the molecule. The polar nature of the molecule means that boiling and melting points of alkyl halides are much higher than alkanes with a similar number of carbons (see pg. 34 in the text)

Uses CFC’s (Chlorofluorocarbons) are used in refrigerators and air conditioners (ex. Freon) (their use is now restricted due to the fact that some of them damage the ozone layer) polymers such as Teflon (non-stick surfaces as in cookware) and PVC (polyvinylchloride) used plumbing DDT (dichlorodiphenyltrichloroethane) – now banned pesticide PCB’s (polychlorinated biphenyls) – electrical transformers

Reactions – Preparing Alkyl Halides Alkenes/Alkynes readily react with halides of acids to form alkyl halides. C=C and C≡ C are weak bonds that are easily broken making molecules that contain them more reactive than alkanes Halogenation (by addition) Ex. C2H4 + HCl → C2H5Cl Substitution reactions with Halogens Ex. benzene + Br → bromobenzene + HBr

Markovnikov’s Rule When Alkene or Alkyne reacts with a hydrogen halide or water the H bonds to the Carbon with the most H already attached. The Rich get Richer! See the

Markovnikov’s Rule Two more examples:

Reactions - Reactions with aromatics Substitution FeCl3 catalyst C6H6 + Cl2 ===========> C6H5Cl + HCl chlorobenzene