What are Organic Halides?
Organic halides are organic compounds composed of a halogen atom bonded to a carbon atom. A halogen (or a salt-former) is an element that has seven outer electrons and can be found in the group seventeen column in the periodic table. Of the five elements in the group, fluorine (F), chlorine (Cl), bromine (Br) and iodine (I) are used in biologicalmolecules. The last and largest halogen,astatine (At), is radioactively unstable and not found in nature. Halogens tend to form ionic compounds with metals such as sodium chloride and covalent compounds with nonmetals to create organohalogens, our main focus. They may also be called organic halides.
Properties of Organic Halides
Physical state and smell
Haloalkanes are generally colorless, sweet-smelling liquids. The lower members with low molecular masses like methyl chloride, methyl bromide and ethyl chloride are colorless gases while members having very high molecular masses are solids.
Solubility
Haloalkanes are practically insoluble in water. This is because they are not able to form hydrogen bonds with water although they are polar in nature. But they are soluble in alcohol, ether, benzene and other organic solvents.
Density
Chloroalkanes are lighter than water while bromides and alkyl iodides are heavier. With the increase in the size of the alkyl group, the densities go on decreasing in the order of :
fluoride > chloride > bromide > iodide.
Boiling Points
The boiling points of alkyl chlorides, bromides and iodides follow the order RI > RBr > RCl where R is an alkyl group. With the increase in the size of halogen, the magnitude of Van der Waals forces increases and, consequently, the boiling points increase. Also, for the same halogen atom, the boiling points of haloalkanes increase with increase in the size of alkyl groups.
The Chemistry Behind Organic Halides
Organic halides are named in one word (non-IUPAC names):
1. The prefix is "organo"
2. The rest of the word is the halogen being used, followed by an "ide" ending
Example: organofluoride or organochloride
Reactivity of Organic Halides
The halogen atom that is bonded to the carbon atom determines the reactivity of the compound. The following is a list of organic halides in order from the highest reactivity to the lowest:
1. Organoiodide
2. Organobromide
3. Organochloride
4. Organofluoride
Note: The most reactive organic halide, organoiodide, is the element that is the lowest in period number on the periodic table and it appears to be the most reactive. As one goes up the periodic table, the reactivity gets smaller and smaller.
Organic halides are divided into two different groups called:
1. Haloalkanes
2. Haloarenes
Haloalkane or alkyl halides
Monohalogen derivatives of alkanes are called haloalkanes or alkyl halides. Their names are derived by naming the attached alkyl group to halogen and adding the name of the halide.
For example,
The common and IUPAC names of a few alkyl halides are given below:
Haloarenes or aryl halides
Haloarenes are halogen derivatives of aromatic hydrocarbons. The aryl halides are compounds where the halogen is attached directly to an aromatic ring and have the general formula ArX, where Ar is an aromatic group. X is the halogen atom.
Haloarenes or aryl halides are named by adding the prefix 'halo' (fluoro, chloro, bromo, iodo) before the name of the aromatic hydrocarbon. In case of di-substituted compounds, the relative positions of the substituents 1,2; 1,3 and 1,4 are indicated by the prefixes ortho (o-), meta (m-) and para (p-) respectively. For example,
The image below shows the electrostatic potential for fluorobenzene (left) and chlorobenzene (right). The higher the electron density, due to lone pairs, the more red an area is. The lower the electron density, the more blue it is. Aryl halides react slowly because of the strength of the C-X bonds.
Pictures
Comments (6)
Gina Lam said
at 2:35 pm on Mar 7, 2010
guys i' ve added something but i don't know if it makes sense lol and does it tie in with this subject? O_o'
Mai Ghannam said
at 10:37 am on Mar 7, 2010
its the same one as my nature and future page
Farzana Afrin said
at 9:56 am on Mar 7, 2010
these two are the websites for the info and the charts but i couldn't find the link for the pic of the periodic table
mai ... try to find the link for the periodic table .
Gina Lam said
at 12:00 am on Mar 7, 2010
and the pictures too
Gina Lam said
at 11:59 pm on Mar 6, 2010
just putthem at the bottom of this page
Gina Lam said
at 11:59 pm on Mar 6, 2010
heyyyy i need the references for this page please and thanks
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