Dibromomethane or methylene bromide, or methylene dibromide is a

halomethane Halomethane compounds are derivatives of methane () with one or more of the hydrogen atoms replaced with halogen atoms (Fluorine, F, Chlorine, Cl, Bromine, Br, or Iodine, I). Halomethanes are both naturally occurring, especially in marine environm ...

with the formula CH₂Br₂. It is slightly soluble in water but very soluble in

organic solvents A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

. It is a colorless liquid.

Physical properties

At ambient temperature, dibromomethane solidifies around 0.61

GPa Grading in education is the application of standardized measurements to evaluate different levels of student achievement in a course. Grades can be expressed as letters (usually A to F), as a range (for example, 1 to 6), percentages, or as num ...

. The crystal structure strongly suggests both interhalogen and hydrogen-halogen interactions.

Preparation

Dibromomethane is prepared commercially from dichloromethane via

bromochloromethane Bromochloromethane or methylene bromochloride and Halon 1011 is a mixed halomethane. It is a heavy low-viscosity liquid with refractive index 1.4808. Halon 1011 was invented for use in fire extinguishers in Germany during the mid-1940s, in an atte ...

: :6 CH₂Cl₂ + 3 Br₂ + 2 Al → 6 CH₂BrCl + 2 AlCl₃ :CH₂Cl₂ + HBr → CH₂BrCl + HCl The latter route requires

aluminium trichloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are col ...

as a catalyst. The bromochloromethane product from either reaction can further react in a similar manner: :6 CH₂BrCl + 3 Br₂ + 2 Al → 6 CH₂Br₂ + 2 AlCl₃ :CH₂BrCl + HBr → CH₂Br₂ + HCl In the laboratory, it is prepared from

bromoform Bromoform is an organic compound with the chemical formula . It is a colorless liquid at room temperature, with a high refractive index and a very high density. Its sweet odor is similar to that of chloroform. It is one of the four haloforms, the ...

using

sodium arsenite Sodium arsenite usually refers to the inorganic compound with the formula NaAsO2. Also called sodium ''meta''-arsenite, it is an inorganic polymer consisting of the infinite chains sO2associated with sodium cations, Na+. The polymer backbone ...

and

sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly corrosive base (chemistry), ...

: :CHBr₃ + Na₃AsO₃ + NaOH → CH₂Br₂ + Na₃AsO₄ + NaBr Another way is to prepare it from

diiodomethane Diiodomethane or methylene iodide, commonly abbreviated "MI", is an organoiodine compound. Diiodomethane is a very dense colorless liquid; however, it decomposes upon exposure to light liberating iodine, which colours samples brownish. It is slig ...

and

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

Uses

Dibromomethane is used as a

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

, gauge fluid, and in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

(often as ¹H-NMR

internal standard In a chemical analysis, the internal standard method involves adding the same amount of a chemical substance to each sample and calibration solution. The internal standard responds proportionally to changes in the analyte and provides a similar, bu ...

). It conviently converts

polyol In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, th ...

s (such as

catechols Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amounts. It ...

) to their

methylenedioxy Methylenedioxy is the term used in the field of chemistry, particularly in organic chemistry, for a functional group with the structural formula which is connected to the rest of a molecule by two chemical bonds. The methylenedioxy group consist ...

derivatives, and bromomethylenates

enolate In organic chemistry, enolates are organic anions derived from the deprotonation of carbonyl () compounds. Rarely isolated, they are widely used as reagents in the Organic synthesis, synthesis of organic compounds. Bonding and structure Enolate ...

s. It is a much cheaper precursor to a Simmons-Smith-type reagent than

Natural occurrence

It is naturally produced by marine

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

and liberated to the oceans. Releasing on soil causes it to evaporate and leach into the ground. Releasing in water causes it to be lost mainly by

volatilisation Pesticide drift, also known as spray drift, is the unintentional diffusion of pesticides toward nontarget species. It is one of the most negative effects of pesticide application. Drift can damage human health, environment, and crops. Together ...

with a half life of 5.2 hours. It has no significant degradation biological or abiological effects. In the atmosphere it will be lost because of reaction with photochemically produced

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

radicals. The estimated half life of this reaction is 213 days.

References

External links

* {{Halomethanes Bromoalkanes Halomethanes Refrigerants