In organic chlorides, chlorine is bonded directly to a carbon atom. The bond is covalent although due to the difference in electronegativity between the two elements it is strongly polarized. For this reason, chlorine can be substituted in many cases in nucleophilic substitution reactions.

Organic chlorides are less flammable than the corresponding hydrocarbons.[4]​ They are often also more toxic. Some chloroalkanes such as dichloromethane are important as solvents. Insecticides such as lindane or DDT are also organic chlorides. Also found in this group are the chlorodibenzodioxins that have become famous and feared due to the Séveso accident.

Chlorides of aliphatic compounds can be obtained by direct reaction of the substance with elemental chlorine. The reaction is usually violent and occurs through a non-selective radical mechanism.

Selectivity can be increased by using N-chlorosucinimide instead of elemental chlorine.

Usually the transformation of another functional group into chloride is more advisable. Thus the hydroxy groups can be replaced by chloride by applying hydrochloric acid (possibly in the presence of zinc chloride as a catalyst), thienyl chloride"), phosphorus chloride, etc.

They can also be obtained by adding chlorine or hydrochloric acid to multiple bonds of alkenes or alkynes. The hydrochloric addition gives mainly the Markownikov product (with the chloride attached to the more substituted carbon) under polar conditions and the anti-Markownikov product (with the chloride on the less substituted carbon) under radical conditions "Radical (chemistry)").

Aromatic chlorides are finally usually obtained by direct chlorination in an electrophilic substitution reaction in the presence of a Lewis acid as a catalyst.

A) Beilstein test:

To determine the presence of chloride in an organic compound, heat a copper wire in a blue flame of a Bunsen burner until no marked coloration is noticeable. It is then contacted with the organic compound and the compound is introduced with the wire into the flame. A bluish-green color indicates the presence of chloride.

Contraindications: Other halides and some amines can give the same reaction.

B) Transformation into inorganic chloride.

A small sample is heated in a test tube with a small amount (few milligrams) of sodium metal (CAUTION EXPLOSIVE REACTIONS MAY OCCUR) until the tube becomes red hot. The tube is then poured into a container with water, acidified with nitric acid and the chloride is precipitated with silver nitrate (AgNO), performing the other tests as described in the case of inorganic chlorides.

Biochemistry

There are few organic chlorides in nature. Therefore, organic chlorides usually have poor biodegradability and remain in the environment for years. Due to their hydrophobic nature, they accumulate in fats, especially in the last links of the food chain and can cause health problems there, which makes chlorides very important for human health.

A chloride ion (diameter 167 pm) is much larger than a chlorine atom (diameter 99 pm). The retention of the chlorine atom in the valence shell is weaker because the chloride anion has one more electron than it.[5]​ The ion is colorless and diamagnetic. In aqueous solution, it is very soluble in most cases; However, some chloride salts, such as silver chloride, lead(II) chloride, and mercury(I) chloride, are only slightly soluble in water.[6] In aqueous solution, the chloride is bound by the protic end of the water molecules.

Chloride can be oxidized but not reduced. The first oxidation, used in the chloralkali process, is the conversion to chlorine gas. Chlorine can be further oxidized to other oxides and oxyanions, including hypochlorite (ClO, the active ingredient in chlorine), chlorine dioxide (ClO), chlorate (), and perchlorate ().

In terms of its acid-base properties, chloride is a weak base, as indicated by the negative pK value of hydrochloric acid. Chloride can be protonated by strong acids, such as sulfuric acid:.

Reaction of ionic chloride salts with other salts to exchange anions. The presence of halide ions such as chloride can be detected using silver nitrate. A solution containing chloride ions will produce a white precipitate of silver chloride:[7]​.

The chloride concentration in an assay can be determined using a chloridometer, which detects silver ions once all of the chloride in the assay has been precipitated by this reaction.

Chlorinated silver electrodes are commonly used in ex vivo electrophysiology.[8]​.

Chlorine can assume oxidation states of −1, +1, +3, +5 or +7. Various neutral chlorine oxides are also known.

Contenido

En la naturaleza, el cloruro se encuentra principalmente en el agua de mar, que tiene una concentración de iones cloruro de 19400 mg/litro.[9]​ En ciertos mares interiores y en pozos subterráneos de salmuera, como el Gran Lago Salado en Utah (EE. UU.) y el Mar Muerto en Israel y Jordania, se encuentran cantidades menores, aunque en concentraciones más altas.[10]​ La mayoría de las sales de cloruro son solubles en agua, por lo que los minerales que contienen cloruro generalmente solo se encuentran en abundancia en climas secos o en las profundidades del subsuelo. Algunos minerales que contienen cloruro incluyen halita (cloruro de sodio NaCl), silvita (cloruro de potasio KCl), bischofita (MgCl∙6HO), carnalita (KCl∙MgCl∙6HO) y kainita (KCl∙MgSO∙3HO). También se encuentra en minerales evaporíticos como la clorapatita y la sodalita.

Role in biology

Chloride has important physiological importance, including the regulation of osmotic pressure, electrolyte balance, and acid-base homeostasis. Chloride is present in all body fluids[11]​ and is the most abundant extracellular anion, accounting for about one-third of the tonicity of the extracellular fluid.[12]​[13]​.

Chloride is an essential electrolyte that plays a key role in maintaining cellular homeostasis and the transmission of action potentials in neurons.[14] It can flow through chloride channels (including the GABA receptor) and is transported by transporters KCC2 and NKCC2.

Chloride is usually (but not always) at a higher extracellular concentration, causing it to have a negative reversal potential (around −61 mV at 37 °C in a mammalian cell).[15] Characteristic concentrations of chloride in model organisms are: in both E. coli and budding yeast they are 10 to 200 mM (depending on the medium), in mammalian cells 5 to 100 mM, and in blood plasma of 100 mM.[16]​.

The concentration of chloride in the blood is called serum chloride and this concentration is regulated by the kidneys. A chloride ion is a structural component of some proteins; for example, it is present in the enzyme amylase. For these functions, chloride is one of the essential dietary minerals (listed by its element name chlorine). Serum chloride levels are regulated primarily by the kidneys through a variety of transporters that are present throughout the nephron.[17]​ Most of the chloride, which is filtered by the glomerulus, is reabsorbed by the proximal and distal tubules (mainly by the proximal tubule) through active and passive transport.[18]​.

Corrosion

The presence of chlorides, such as in seawater, significantly worsens the pitting corrosion conditions of most metals (including stainless steels, aluminum, and high-alloy materials). Chloride-induced corrosion of steel in concrete causes a local degradation of the protective oxide form in alkaline concrete, so that a subsequent localized corrosion attack occurs.[19]​.

Environmental threats

The increase in chloride concentrations can cause a series of ecological effects in both the aquatic and terrestrial environments. It can contribute to the acidification of streams, mobilize radioactive metals from the soil through ion exchange, affect the mortality and reproduction of aquatic plants and animals, promote the invasion of saltwater organisms into formerly freshwater environments, and interfere with the natural mixing of lakes. Sodium chloride has also been shown to change the composition of microbial species at relatively low concentrations. It can also hinder the denitrification process, a microbial process essential for nitrate removal and water quality conservation, and inhibit nitrification and respiration of organic matter.[20]​.

In organic chlorides, chlorine is bonded directly to a carbon atom. The bond is covalent although due to the difference in electronegativity between the two elements it is strongly polarized. For this reason, chlorine can be substituted in many cases in nucleophilic substitution reactions.

Organic chlorides are less flammable than the corresponding hydrocarbons.[4]​ They are often also more toxic. Some chloroalkanes such as dichloromethane are important as solvents. Insecticides such as lindane or DDT are also organic chlorides. Also found in this group are the chlorodibenzodioxins that have become famous and feared due to the Séveso accident.

Chlorides of aliphatic compounds can be obtained by direct reaction of the substance with elemental chlorine. The reaction is usually violent and occurs through a non-selective radical mechanism.

Selectivity can be increased by using N-chlorosucinimide instead of elemental chlorine.

Usually the transformation of another functional group into chloride is more advisable. Thus the hydroxy groups can be replaced by chloride by applying hydrochloric acid (possibly in the presence of zinc chloride as a catalyst), thienyl chloride"), phosphorus chloride, etc.

They can also be obtained by adding chlorine or hydrochloric acid to multiple bonds of alkenes or alkynes. The hydrochloric addition gives mainly the Markownikov product (with the chloride attached to the more substituted carbon) under polar conditions and the anti-Markownikov product (with the chloride on the less substituted carbon) under radical conditions "Radical (chemistry)").

Aromatic chlorides are finally usually obtained by direct chlorination in an electrophilic substitution reaction in the presence of a Lewis acid as a catalyst.

A) Beilstein test:

To determine the presence of chloride in an organic compound, heat a copper wire in a blue flame of a Bunsen burner until no marked coloration is noticeable. It is then contacted with the organic compound and the compound is introduced with the wire into the flame. A bluish-green color indicates the presence of chloride.

Contraindications: Other halides and some amines can give the same reaction.

B) Transformation into inorganic chloride.

A small sample is heated in a test tube with a small amount (few milligrams) of sodium metal (CAUTION EXPLOSIVE REACTIONS MAY OCCUR) until the tube becomes red hot. The tube is then poured into a container with water, acidified with nitric acid and the chloride is precipitated with silver nitrate (AgNO), performing the other tests as described in the case of inorganic chlorides.

Biochemistry

There are few organic chlorides in nature. Therefore, organic chlorides usually have poor biodegradability and remain in the environment for years. Due to their hydrophobic nature, they accumulate in fats, especially in the last links of the food chain and can cause health problems there, which makes chlorides very important for human health.

A chloride ion (diameter 167 pm) is much larger than a chlorine atom (diameter 99 pm). The retention of the chlorine atom in the valence shell is weaker because the chloride anion has one more electron than it.[5]​ The ion is colorless and diamagnetic. In aqueous solution, it is very soluble in most cases; However, some chloride salts, such as silver chloride, lead(II) chloride, and mercury(I) chloride, are only slightly soluble in water.[6] In aqueous solution, the chloride is bound by the protic end of the water molecules.

Chloride can be oxidized but not reduced. The first oxidation, used in the chloralkali process, is the conversion to chlorine gas. Chlorine can be further oxidized to other oxides and oxyanions, including hypochlorite (ClO, the active ingredient in chlorine), chlorine dioxide (ClO), chlorate (), and perchlorate ().

In terms of its acid-base properties, chloride is a weak base, as indicated by the negative pK value of hydrochloric acid. Chloride can be protonated by strong acids, such as sulfuric acid:.

Reaction of ionic chloride salts with other salts to exchange anions. The presence of halide ions such as chloride can be detected using silver nitrate. A solution containing chloride ions will produce a white precipitate of silver chloride:[7]​.

The chloride concentration in an assay can be determined using a chloridometer, which detects silver ions once all of the chloride in the assay has been precipitated by this reaction.

Chlorinated silver electrodes are commonly used in ex vivo electrophysiology.[8]​.

Chlorine can assume oxidation states of −1, +1, +3, +5 or +7. Various neutral chlorine oxides are also known.

Contenido

En la naturaleza, el cloruro se encuentra principalmente en el agua de mar, que tiene una concentración de iones cloruro de 19400 mg/litro.[9]​ En ciertos mares interiores y en pozos subterráneos de salmuera, como el Gran Lago Salado en Utah (EE. UU.) y el Mar Muerto en Israel y Jordania, se encuentran cantidades menores, aunque en concentraciones más altas.[10]​ La mayoría de las sales de cloruro son solubles en agua, por lo que los minerales que contienen cloruro generalmente solo se encuentran en abundancia en climas secos o en las profundidades del subsuelo. Algunos minerales que contienen cloruro incluyen halita (cloruro de sodio NaCl), silvita (cloruro de potasio KCl), bischofita (MgCl∙6HO), carnalita (KCl∙MgCl∙6HO) y kainita (KCl∙MgSO∙3HO). También se encuentra en minerales evaporíticos como la clorapatita y la sodalita.

Role in biology

Chloride has important physiological importance, including the regulation of osmotic pressure, electrolyte balance, and acid-base homeostasis. Chloride is present in all body fluids[11]​ and is the most abundant extracellular anion, accounting for about one-third of the tonicity of the extracellular fluid.[12]​[13]​.

Chloride is an essential electrolyte that plays a key role in maintaining cellular homeostasis and the transmission of action potentials in neurons.[14] It can flow through chloride channels (including the GABA receptor) and is transported by transporters KCC2 and NKCC2.

Chloride is usually (but not always) at a higher extracellular concentration, causing it to have a negative reversal potential (around −61 mV at 37 °C in a mammalian cell).[15] Characteristic concentrations of chloride in model organisms are: in both E. coli and budding yeast they are 10 to 200 mM (depending on the medium), in mammalian cells 5 to 100 mM, and in blood plasma of 100 mM.[16]​.

The concentration of chloride in the blood is called serum chloride and this concentration is regulated by the kidneys. A chloride ion is a structural component of some proteins; for example, it is present in the enzyme amylase. For these functions, chloride is one of the essential dietary minerals (listed by its element name chlorine). Serum chloride levels are regulated primarily by the kidneys through a variety of transporters that are present throughout the nephron.[17]​ Most of the chloride, which is filtered by the glomerulus, is reabsorbed by the proximal and distal tubules (mainly by the proximal tubule) through active and passive transport.[18]​.

Corrosion

The presence of chlorides, such as in seawater, significantly worsens the pitting corrosion conditions of most metals (including stainless steels, aluminum, and high-alloy materials). Chloride-induced corrosion of steel in concrete causes a local degradation of the protective oxide form in alkaline concrete, so that a subsequent localized corrosion attack occurs.[19]​.

Environmental threats

The increase in chloride concentrations can cause a series of ecological effects in both the aquatic and terrestrial environments. It can contribute to the acidification of streams, mobilize radioactive metals from the soil through ion exchange, affect the mortality and reproduction of aquatic plants and animals, promote the invasion of saltwater organisms into formerly freshwater environments, and interfere with the natural mixing of lakes. Sodium chloride has also been shown to change the composition of microbial species at relatively low concentrations. It can also hinder the denitrification process, a microbial process essential for nitrate removal and water quality conservation, and inhibit nitrification and respiration of organic matter.[20]​.