What are the chemical properties of bromine

bromine

discovery

The element bromine was discovered by Antoine-Jérôme Balard in 1826 while studying marine algae. Justus Liebig was already isolating bromine from brine two years earlier, but did not notice that he had discovered a new element.

Occurrence

The very reactive halogen is hardly present as a free element if one is aware of traces of Br2 disregards in the earth's atmosphere. In contrast, it is found in bound form in many salts, especially in bromides and bromates. The most important bromide is probably potassium bromide. In addition to NaCl, the rock salt stores mainly contain KCl and MgCl2. Bromine makes up less than 0.001% of the earth's crust, while chlorine is 250 times more common in salt deposits. Sea water contains approx. 0.0065% bromide, the Dead Sea, however, has a bromide content of up to 1.5% (Lexikon der Chemie).

presentation

In the laboratory, bromine is produced by the reaction of conc. Sulfuric acid and manganese dioxide obtained with potassium bromide. Hydrogen bromide HBr is initially formed from sulfuric acid and potassium bromide (analogous to the production of hydrogen chloride from concentrated sulfuric acid and sodium chloride), and this then reacts with the manganese dioxide according to the following equation:

Manufacturing

In industry, bromine is produced by the oxidation of bromide solutions with chlorine - a typical redox reaction in which non-metals are involved and which also plays an important role in chemistry lessons when the redox potentials of halogens are explained in upper school:

properties
Physical Properties

Bromine is a deep brown, pungent and suffocating smelling liquid at room temperature. Besides mercury, bromine is the only element that is liquid at room temperature. The density of liquid bromine is 3.12 g / cm2 and is therefore quite high for a liquid. Solid bromine is characterized by a slightly metallic sheen.

Bromine is sparingly soluble in water (3.55 g of bromine in 100 ml of water at room temperature); bromine water is then formed, which is often used as a substitute for pure bromine in experiments in schools. In contrast, bromine is very soluble in organic solvents due to its completely non-polar structure.

chemical properties

Like chlorine, bromine is extremely reactive; it reacts with most elements and with many compounds, including organic compounds.

Reaction with metals

With metals, bromine forms salts, namely the bromide, in mostly exothermic reactions. The more noble the metal, the less exothermic the reaction is. The reaction with alkali metals and alkaline earth metals already takes place at room temperature, more noble metals such as copper or silver have to be heated to a greater or lesser extent so that they react with chlorine. Moist (water-containing) bromine reacts with metals much more violently than pure bromine. Tantalum and platinum are the only metals that do not react even with moist bromine (Wikipedia).

Reaction with non-metals

With hydrogen, chlorine forms the strong acid hydrogen chloride HCl, the aqueous solution of which is known as hydrochloric acid. This reaction is also extremely exothermic (chlorine-oxyhydrogen gas reaction). Chlorine hardly or not at all reacts with other non-metals.

Reaction with organic compounds

Bromine reacts with alkanes and alkyl compounds in a radical substitution reaction to form haloalkanes. Electrophilic addition occurs with alkenes and alkynes, and electrophilic substitution is possible with aromatics if a suitable catalyst is present.

use

Bromine is mainly used in organic chemistry to carry out substitutions or additions to hydrocarbons or other organic compounds. These reactions play an important role in the production of fuel additives, flame retardants, pesticides, tear gas and so on.

The compound hexabromocyclododecane has made headlines recently because it is added to the plastic Styrofoam as a flame retardant. Hexabromocyclododecane is now considered highly toxic and difficult to degrade, which has driven up the prices for styrofoam disposal. The disposal of a ton of Styrofoam now costs more than 9,000 euros in some cases - and all because of the bromine in the flame retardant.