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Chloroethane

During early 80’s and before that, the chloroethane presence was detected in outdoor air. Most of the cities and even in suburban areas the average air contamination for chloroethane was found to be 40 to 140 ppt. This was lesser than 5 ppt in rural areas. The lower production of this particular gas in every continent has helped reduce the level but it persists in some countries even now. 

Although there is not much of information available but there is a chance of this gas presence in drinking water albeit in very low levels. The exposure to various paints, solvents and refrigerants that we come across on a daily basis exposes the general population to this hazardous chemical resulting in difficult medical and para medical conditions.

 

Chloroethane Formula

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The actual formula for chloroethane should be dichloroethane, where there is a presence of two chlorine atoms in the main chain of ethane. The two hydrogen atoms of the ethane molecule are replaced by two chlorine atoms and thus the name di (two) chloroethane.

The first of the series should be 1, 1 dichloroethane, which shows the two hydrogen in two main chain carbon getting replaced by chlorine atoms. This molecule is detected very in low levels indoor and outdoor air but is found to be higher in occupational settings of factories or even in food packaging materials, adhesives etc. 
1,1-Dichloro Ethane
 
These molecules are also found in hazardous waste sites as well as in the coatings for steel pipes. Next to 1 1 di chloroethane we can also have a very common compound involving the same combination but arranged in a different way. The molecule is 1 2 di chloroethane, and is detected in almost all urban household as well as in the vicinity of hazardous waste sites as well as ambient air samples of factories. 
 
The next molecule of the chloroethane series is 1,1,1-tricholorethane.

Trichloro Ethane
 
The global atmospheric concentration is calculated to be around 1.5 ppb by 2030. The long life of this molecule allows it to travel to long distance from the initial point of release. This molecule is also detected near newly constructed buildings as well as in rivers and lakes along with soil which are flushed with the washing bed areas of these sites. 

Chloroethane structural formula

The structural formula for the above mentioned molecules of chloroethane are as follows:

1,1 - di chloroethane. 
Dichloro Ethane
 
1,2 - di chloroethane (chair form). 
1,2-Dichloro Ethane
 
1,2 - di chloroethane (boat form).
 Dichloro Ethane (Boat Form)

Chloroethane Properties

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Very less information is available for the chloroethane molecule. The only specific properties that we could make out is the photo oxidation in atmosphere and hydrolysis. The main process cannot be identified by certain. Chloroethane is also detected in finishing part of drinking water and is also present in atmosphere due to the small amount of this gas escaping into during photo oxidation.

The photo oxidation takes place in troposphere and based on the process there are several physical properties that we get to see for these molecules.

The general physical properties like molecular mass, melting point and boiling point of chloroethane are as follows: 
  • Molecular mass of chloroethane is 64.5 g
  • Melting point of chloroethane is – 134.4 C 
  • Boiling point of chloroethane (1 atm) is 12.3 C
  • The vapour pressure of chloroethane at around 20 C is found to be 1000 Torricelli.  
  • The solubility of chloroethane in water at 20 C is found to be 5740 mg per litre. 
Photo dissociation in terrestrial environment is not expected to take place for chloroethane as this compound doesn’t have any chromophores which helps in absorbing the visible range light or near ultra violet region light of the electromagnetic spectrum.
The rate of reaction of chloroethane with hydroxyl radicals in troposphere is comparatively rapid and in case it is kept unreacted, it will undergo photo dissociation due to presence of high energy short wavelength of ultra violet spectrum. 

Oxidation
The indirect evidence of low potential oxidation in aquatic system is available for chloroethane. There is a large excess of dissolved oxygen in the isomeric forms of chloroethane is due to ionic hydrolysis rather than oxidation. Oxidation is slower than loss by volatization.

Due to high vapour pressure of chloroethane, volatization to atmosphere is expected to be quite rapid. The fraction of troposphere chloroethane eventually reaching the stratosphere through diffusion is less than one percent and troposphere to stratosphere turn over time is almost close to 30 years.

Hydrolysis
Hydrolytic life or rather half-life is calculated as 40 days for chloroethane. The short hydrolytic life and high solubility in water of chloroethane shows that hydrolysis may be an important fate process for the compound. 

Volatilization 
The experimental half-life for volatization of chloroethane as 21 minutes while by removing 90 percent of chloroethane under same conditions might take 79 minutes. For chloro aliphatic in general the stirring speed has specific effect on the volatization rate. When the intermittent stirring of 15 seconds duration for every five minutes and it takes almost 90 minutes for complete depletion.   

Bioaccumulation
Polar molecules are more prone to biodegradation and the non-polar varieties start accumulating as these molecules lack the solvency capacity. Bioaccumulation is basically a octanol / water partition coefficient of the compound which indicates that chloroethane may not bio accumulate to an significant limits.

Biotransformation and biodegradation
There is no specific data available for chloroethane biodegradation in aquatic systems but in completely sealed systems biological oxygen demand there is a chance of getting a specific reading for the volatile chloroethane. This study also showed that significant oxygen absorption from these compounds slows down the entire biodegradation process. 

Chloroethane Polar or Nonpolar

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The molecular structure of chloroethane shows a polar characteristics and this is mainly due to the presence of permanent dipole – dipole interaction. This dipole – dipole interaction doesn’t give out enough energy to overcome the water molecule’s strong hydrogen bonds. In any non-polar molecule the electrons are distributed uniformly but in case of a polar molecule like chloroethane the electrons at any instance are distributed closer to any of the atom in the molecule or may be present in any one side of the molecule. A temporary dipole is present which exerts an influence on the molecules of vicinity. This results in an induced dipole and the resultant attractive force existing between a temporary dipole and an induced dipole are called London forces. 

The ease with which an electron cloud is distorted by nearby charges or the dipoles is called polarizability. The attractive forces between temporary dipoles in a non-polar molecule are found to be small and short lifetime. 

The electrons which are far from atomic nuclei are more easily distorted or polarized than electrons that are closer to the atomic nuclei. The same polar characteristics is applied for the molecules physical attributes as well. The boiling point of bromoethane is higher than chloroethane because the C – Cl is found to be more polar than C – Br and hence that proves that polarity is not the only issue to determine the higher or lower boiling point. The molecular weights are different as well and the electrons of the bigger is more polarizing than the electrons of chlorine atom. The order of boiling point shows the polarization of a particular molecule and London attractive forces.

$CH_{3}CH_{2}Cl$ ----- 12.3 C, has a molecular weight of 64.5 amu

$CH_{3}CH_{2}Br$ ----- 38.4 C has molecular weight of 109 amu

Even when these molecules have similar type of atoms, the London forces are different due to difference in molecular weight. The London forces are also dependent on molecular shapes as the spherical shapes have less polarizing effect than the ones which carry an ellipsoidal shape. 

Uses of Chloroethane

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The chloroethane molecule is used many of the chemical processes we get to see around us. 
  • It is used as an intermediate in many chemical processes 
  • It is used in many of the essential solvents for everyday use
  • It is used as an ingredient for aerosol and mainstream anaesthesia 
  • Chloroethane is also used as an main ingredient for foamed plastic 
  • It is also used in tetra ethyl lead production 
  • Chloroethane is also used as an additive for leaded petroleum products to reduce knocking effect
  • Chloroethane is used as miscellaneous substance for the production of ethyl cellulose 
  • Chloroethane is used as local numbing agent before injectable are pushed in or before any body piercing is carried out
  • Chloroethane is used as an agent for refrigerant purpose 
  • Chloroethane is used in dentistry to test pulp vitality testing
  • Chloroethane is used in medical science as to counter the effect of irritation in visceral pain syndrome 
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