HALOGENATED ORGANIC COMPOUNDS AS AN INTEGRAL PART OF THE WORLD AROUND US

Throughout our journey of scientific dissemination we have been working with the organization of the family of organic compounds, at this point we will be working on how these compounds work when they are substituted with a halogen, since the combination of hydrocarbons with some of the most electronegative elements of the periodic table generate compounds that are widespread in nature and have a large number of applications in modern industrial processes.

Consequently, we will be working with alkyl halides and how the chemical formation of these compounds provides a diversity of scientific applications that have generated a direct impact on the society in which we live.

At this point, an alkyl halide is formed from a hydrocarbon that has been subjected to a halogenation process where the electronegative group or halogen enters certain carbons to form these new compounds that are present in algae and in different marine organisms, also in forest fires and volcanoes have been recorded increasing concentrations of these substances, Hence, with the development of scientific advances it has been possible to generate applications for these compounds, so that they are widely used in the manufacture of industrial solvents, as well as their use in inhaled anesthetics in the medical field or in the generation of refrigerants, without neglecting their organic uses at the agricultural level, such as their implementation in the manufacture of pesticides.

Apart from the above, through the modern and technological evolution that we are living these compounds have received a greater boom, as they are being implemented as solvents in different industrial processes, an example of this is represented by trichloroethylene highly demanded to clean semiconductor chips and other compounds.

Similarly, other compounds belonging to the alkyl halides have been identified and have impressive medical potential, for example the usefulness of epibatidine, which has been isolated in the skin of frogs from Ecuador and has been demonstrating a potential greater than 200 times over morphine to block pain in animals, hence the study of the chemistry of this family of compounds is necessary to understand the chemical behavior and its interaction with metabolic processes or otherwise practical associated with human development.

Therefore, by focusing our attention on the chemical structuring behind alkyl halides we can realize that the carbon-halogen bond that forms is nothing more than the result of an overlap in the sp3 orbital of the carbon with an orbital from the halogen, Hence, the carbon atoms within the halides have an approximately tetrahedral geometry with a bond angle close to 109 degrees, so that the alkyl halides when going down in the periodic table and in reference to the halogen, tend to be much smaller, which implies that the resistance of these compounds decreases according to the presence of the halogen present.

In such a way that the carbon - halogen bond is considered as a polar bond where the carbon atom tends to form a positive charge and the halogen a slightly negative charge, product of the electronic displacement made by an electronegative element on the carbon atom, hence the dipole moment that is presented is appreciable so that all halides must behave as an electrophile in polar reactions, hence much of the chemistry of these compounds is determined by this electrophilic behavior.

In this sense, the chemistry behind the process of preparation of alkyl halides consists of a process of reactions among which stand out the presence of alkenes and their electrophilic addition reactions that respect the Markovnikov addition rules, likewise, we can find reaction methods through an alkane where through the reaction route of radicals in chains, the respective halide can be obtained. Consequently, and although alkanes are usually inert, they react very easily in the presence of chlorine or bromine and sunlight forming a haloalkane that follows a synthetic substitution route.

However, it is necessary to understand that from the point of view of the reaction mechanism, the halogenation of alkanes is a bad method in a synthetic process, since several free radicals are generated, which slows down the reaction process and consequently, when multiple halogenations are needed, the process is extremely slow.

So starting from the above, it is necessary to understand that the presence of these organic compounds in nature is increasing, so that the natural halide organ until 1968 had only managed to identify a little more than 30 compounds of this type.

At that time, it was assumed that chloroform, phenols, chlorinated aromatic compounds of the polychlorinated biphenyl type and other substances found in the environment, were polluting substances. Today, with the substantial advances in chemistry and science in general, the thinking is different and consequently has changed, so that more than 3000 halogenated organ compounds have been identified in nature and it is certain that there are many more.

So that in various bio-ecosystems of our planet, we can find small compounds such as chloromethane, to much more complex formations, hence their presence in plants, bacteria and animals is no surprise at the scientific level since many of these organic compounds have a specific biological activity.

An example of this is represented by the brominated substance Jasplaquinolide, which was discovered by Philip Crews, which is capable of interrupting the formation of actin microtubules that form the skeleton of cellular organisms, it is also possible to identify this type of compound in worms of the acorn species located in Okinawa in a study area of 1 square kilometer, which shows that in that space an approximate of almost 100 pounds of halogenated phenols are released per day, hence the release of this type of compounds that at first were considered toxic are in response to the organisms use it as self-defense, as a mechanism to scare away predators or otherwise for being irritating to them, although they have also been identified as natural pesticides.

We can also identify the presence of these compounds in humans, since we have the ability to produce them as part of our defense against infections, where the immune system is endowed with peroxidase enzymes capable of performing halogenation reactions where the presence of fungi and bacteria are involved, so that it attacks and eliminates them as pathogens.

Consequently, there is still much to learn about these organic compounds and their presence in the natural habitat, but what we are sure of is that through scientific advances we have realized that halogenated organic compounds are an integral part of the world around us.

[1] Chang, R. (2010). Química. Decima edicion. McGraw-hill Interamericana editores. ISBN: 978-607-15-0307-7.

[2] Ralph, H. Petrucci, William S. Harwood, E. Geoffrey Herring. (2003). QUIMICA GENERAL. Octava edición. PEARSON EDUCACIÓN. S.A., Madrid.

[3] WADE,LEROY. (2011). . ORGANIC CHEMISTRY. VOLUME 2. SEVENTH EDITION. PEARSON EDUCATION, MEXICO, 2011 ISBN: 978-607-32.()793-5.

1. The molecular models presented were designed by @madridbg using Chem3D and Chemdraw software.

2. For more information related to the areas of science, technology, engineering and mathematics, do not hesitate to visit #stemsocial and #stem-espanol, they are communities that promote scientific advances in these areas