| Chemical Properties | Benzyl bromide is an aromatic compound in which the benzene ring substituted with a bromomethyl group, and is produced by the reaction of toluene with bromine in the presence of an oxidizing agent. It is a combustible, colorless to yellow liquid with a pleasant odor. insoluble in water and easily soluble in most organic solvents. Has a strong tearing effect and unpleasant pungent odor, minimum irritant concentration of 4 mg/m3, intolerable concentration of 50-60 mg/m3. |
| Uses | Making foaming and frothing agents, organic synthesis. |
| Uses | Benzyl bromide is widely useful in organic synthesis as a benzyl protecting group for alcohols and carboxylic acids. It is used in the preparation of foaming and frothing agents, quaternary ammonium compounds, peniclins, photographic chemicals, synthetic resins, dyes and plasticizers and esters. It is also involved in the synthesis of (E)-(2-Iodovinyl)benzene by reacting it with diiodomethane. |
| Definition | ChEBI: Benzyl bromide is a member of the class of benzyl bromides that is toluene substituted on the alpha-carbon with bromine. It has a role as a lachrymator. |
| Preparation | Benzyl bromide is synthesized by toluene bromination. Toluene heated to 50°C, add bromine reaction, the reaction temperature of 75-80°C, reaction 6h, fractional distillation at atmospheric pressure to remove the fraction before 140°C, and then distillation under reduced pressure, collect 112-114°C(2.0kPa) fraction, to get benzyl bromide. |
| Application | Benzyl bromide is an aromatic halide that is mainly used as a protecting agent for protecting hydroxy group of alcohols via O-benzylation reaction. It has been used as an initiator in the synthesis of poly(styrene-b-methylmethacrylate) copolymers by atom transfer radical polymerization. It can undergo Menschutkin reaction with 1, 2-dimethylimidazole to form 3-benzyl-1, 2-dimethylimidazolium bromide. |
| Synthesis Reference(s) | Journal of the American Chemical Society, 95, p. 3412, 1973 DOI: 10.1021/ja00791a072
Tetrahedron Letters, 29, p. 707, 1988 DOI: 10.1016/S0040-4039(00)80190-2
The Journal of Organic Chemistry, 51, p. 929, 1986 DOI: 10.1021/jo00356a032 |
| General Description | Benzyl bromide appears as a colorless liquid with an agreeable odor. Toxic by inhalation and by skin absorption. It is slightly soluble in water and denser than water (density 1.44 g / cm3 (Aldrich)). A lachrymator. Corrosive to metals and tissue. |
| Air & Water Reactions | Sensitive to exposure to light and moisture. Slightly soluble in water. |
| Reactivity Profile | Benzyl bromide reacts with water, alcohols, common metals (except nickel and lead), bases, amines and oxidizing agents. . Benzyl bromide stored over activated 4A molecular sieve burst a bottle due to condensation-polymerization reaction with generation of HBr gas, [Chem. Eng. News, 1979, 57(12), 74]. |
| Hazard | Highly toxic. Corrosive to skin and tissue. A lachrymator. |
| Health Hazard | Inhalation causes irritation of nose and throat; severe exposure may cause pulmonary edema. Vapors cause severe eye irritation; liquid can burn eyes. Skin contact causes irritation. Ingestion causes irritation of mouth and stomach. |
| Chemical Reactivity | Reactivity with Water Reacts slowly generating hydrogen bromide (hydrobromic acid); Reactivity with Common Materials: Decomposes rapidly in the presence of all common metals except nickel and lead, liberating heat and hydrogen bromide; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Rinse with sodium bicarbonate or lime solution; Polymerization: Polymerizes with evolution of heat and hydrogen bromide when in presence with all common metals except nickel and lead; Inhibitor of Polymerization: None. |
| Safety Profile | Intensely irritating and corrosiveto skin, eyes, and mucous membranes. Large doses causecentral nervous system depression. Mutation datareported. Reaction with molecular sieve produces toxichydrogen bromide gas. |
| Potential Exposure | It is used as a chemical intermediate; in organic syntheses; as a foaming and frothing agent. |
| Shipping | UN1737 Benzyl Bromide, Hazard class: 6.1; Labels: 6.1—Poisonous materials, 8—Corrosive material. |
| Purification Methods | Wash benzyl chloride with conc H2SO4 (CARE), water, 10% Na2CO3 or NaHCO3 solution, and again with water. Dry it with CaCl2, Na2CO3 or MgSO4 and fractionally distil it in the dark, under reduced pressure. It has also been thoroughly degassed at 10-6 mm and redistilled in the dark. This gives material with max (MeCN): 226nm ( 8200) [Mohammed & Kosower J Am Chem Soc 93 2709 1971]. [Beilstein 5 IV 829.] Handle in a fume cupboard, extremely LACHRYMATORY. |
| Incompatibilities | May form explosive mixture with air. Contact with water forms hydrogen bromide and benzyl alcohol. Incompatible with strong oxidizers, bases, magnesium. Attacks metals, except nickel and lead, in the presence of moisture. |
| Waste Disposal | Pour into vermiculite, sodium bicarbonate, or a sand-soda ash mixture and transfer to paper boxes, then to an open incinerator. Alternatively, mix Benzyl Bromide 417 with flammable solvent and spray into incinerator equipped with after burner and alkali scrubber. |
