Description
Benzyl bromide is a combustible, colorless toyellow liquid with a pleasant odor. Molecularweight=171.05;Specific gravity (H2O:1) =1.438; Boilingpoint= 198℃; Freezing/Melting point =-4.0℃;Flashpoint =79℃ (cc). Hazard Identification (based on NFPA-704 M Rating System): Health 3, Flammability 2,Reactivity 1. Insoluble in water (slowly decomposes).
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.
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.
First aid
If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contactsthe skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attentionimmediately. If this chemical has been inhaled, removefrom exposure, begin rescue breathing (using universalprecautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transferpromptly to a medical facility. When this chemical hasbeen swallowed, get medical attention. If victim is conscious,administer water or milk. Do not induce vomiting.Medical observation is recommended for 24 48 h afterbreathing overexposure, as pulmonary edema may bedelayed. As first aid for pulmonary edema, a doctor orauthorized paramedic may consider administering a corticosteroid spray
storage
Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Color Code—White: Corrosiveor Contact Hazard; Store separately in a corrosion-resistantlocation. Store in tightly closed containers in a cool, wellventilated area away from water and other incompatiblematerials listed above.
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.
