Alkyl Halide Syntheses

Alkyl Halide Syntheses

You may use these summaries and problems but you may NOT download them for use at another site, nor may you charge for access to them. Copyright Linda M. Sweeting 1997

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From Alcohols: Nucleophilic Substitution

Mechanism!; SN2; other reagents HCl, HI, H2SO4

McMurry 10.7, Fessenden 7.4-7.6, Schmid 11.17, 12.9

Mechanism!; SN1; other reagents HCl, HI

McMurry 7.1, 10.7, 11.9, Fessenden 7.4-7.6, Schmid 11.17, 12.10, 12.16,

Intermediate is ROSOCl, the half-ester; the reaction is stereospecific.

The reaction of PCl3 and PBr3 is similar; no rearrangements.

McMurry 10.7, Fessenden 7.5, Schmid 11.17,

From Alkenes by Addition

Mechanism! May result in carbocation rearrangements.

McMurry 6.8, 6.9, Fessenden 10.6, Schmid 7.8 – 7.17,

Mechanism! Note that peroxides need to be present at the same time as the HBr for this free-radical anti-Markovnikov addition.

McMurry 5.1, 5.6, 7.5, Fessenden 10.6, Schmid 18.5 – 18.6

Mc Murry 7.5, Fessenden 10.6, Schmid 8.1 – 8.4

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Mechanism! Stereospecific!

Note that I2 adds like Br2; Cl2 adds too but is not stereospecific as it is too electronegative and too small to form a “chloronium” ion. F2 reacts explosively.

McMurry 10.10, Fessenden 10.9, Schmid 8.8

Mechanism! Stereospecific!

McMurry 7.3, Fessenden 10.10, Schmid 8.9,

From Alkanes

Mechanism! Free radical reaction produces the most substituted halide in the highest concentration. Reaction accelerated by heat and/or light.

McMurry 5.1, 10.4, Fessenden 6.1-6.6, Schmid 18.1 – 18.4,

An adjacent carbon-carbon double bond or aromatic ring stabilizes the intermediate radicals (allyl and benzyl) and makes reaction at these sites easier than tertiary.

McMurry 10.5, 10.6, Fessenden 6.5, Schmid 19.3, 20.9A,

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