ALKYL HALIDES AND ARYL HALIDES PDF DOWNLOAD!
In general, aryl halides (C6H5-X or Ar-Xwhere X = F, Cl, Br and I) are much less reactive than simple alkyl halides since they do not usually undergo simple. ORGANIC CHEMISTRY. Alkyl Halides and Aryl Halides. Dr. Anju Srivastava. Dept. of Chemistry. Hindu College. Delhi. . CONTENTS. Alkyl Halides. Benzylic Halides, Allylic Halides, Vinylic Halides, and Aryl Halides. The functional group of alkyl halides is a carbon-halogen bond, the common halogens being fluorine, chlorine, bromine and iodine. With the exception of iodine, these halogens have electronegativities significantly greater than carbon.
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If one or more hydrogen atom is replaced in hydrocarbon by equivalent number of halogen, the compounds obtained are called halogen derivatives of hydrocarbons.
Halogen derivatives of hydrocarbons are further classified as aliphatic halogen compounds and aromatic halogen compounds. Unlike in other substitution reactions, fluoride is the best leaving group, and iodide the worst, due to the fluoride's high electronegativity allowing better stabilization of the negatively charged intermediate.
Alkyl & Aryl Halides - Study Material for IIT JEE | askIITians
Benzyne[ edit ] Aryl halides are capable of doing reactions via the benzyne mechanism, involving sodium amide in liquid ammonia. For example, chlorobenzene can be converted to aniline under these conditions.
Organometallic reagent formation[ edit ] Aryl halides react with metals, generally lithium or magnesiumto give more reactive derivatives that behave as sources of aryl anions. Direct formation of Grignard reagentsby adding the magnesium to the aryl halide in an ethereal solution, works well if the aromatic ring is not significantly deactivated by electron-withdrawing groups.
Compounds such as para-bromonitrobenzene cannot form stable Grignards directly, as their aromatic rings are too deactivated. If such a Grignard is needed, it's usually made by magnesium-halogen exchange involving isopropyl alkyl halides and aryl halides chloride at oC.
Chemistry - Introduction to Alkyl and Aryl Halides
This reaction takes place because the pKa of the aromatic protons is much lower—generally around 45, while that of the aliphatic alkane exceeds The Grignards made using this procedure are generally used immediately, to avoid decomposition.
Other reactions[ edit ] The halides can be displaced by alkyl halides and aryl halides nucleophiles via reactions involving radical anions.
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- 8.7: Benzylic Halides, Allylic Halides, Vinylic Halides, and Aryl Halides
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Alternatively aryl halides, especially the bromides and iodides, undergo oxidative additionand thus are subject to Buchwald—Hartwig amination -type reactions. Fluorobenzene The image to the left shows the alkyl halides and aryl halides potential for fluorobenzene and to the right chlorobenzene The more red an area is, the higher the electron density and the more blue an area is, the lower the electron density.
The halogen atom is a region of high electron density red due to the lone pairs red.