Benzyl bromide

Description

Benzyl bromide is typically used for installing benzyl protecting groups on alcohols and amines. Benzyl bromide is a strong lachrymator and should be handled in a fume hood. Concentrating reaction mixtures on rotovaps that are not in a fume hood can lead to enough exposure for the irritating effects to be noticed. Purifying crude reaction material on automated purification machines outside a fume hood can also provide sufficient exposure to notice the effects (irritated eyes, coughing, etc.).

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.

The Uses of Benzyl bromide

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.

The Uses of Benzyl bromide

To a solution of the SM (10.0 g, 99.0 mmol) in ACN (300 mL) was added K2CO3 (39.4 g, 285 mmol) and BnBr (41.0 mL, 346.0 mmol). The reaction mixture was stirred at reflux for 3 h. Upon completion, the reaction mixture was quenched with H2O, extracted with EtOAc, dried (Na2SO4), and concentrated. The resulting material was purified by silica gel column chromatography (10% EtOAc/hexane) to provide the product as a white solid. [30 g, 78%]

The Uses of Benzyl bromide

Making foaming and frothing agents, organic synthesis.

What are the applications of Application

Benzyl bromide is a reagent and building block consisting of a benzene ring substituted with a bromomethyl group

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.

What are the applications of 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.

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.

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.

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.