Why ethylenedichloride not miscible with water?

Question

there are two chloride ions on the molecule which more electronegative than carbon.Whether It will contribute towards the polarity of the molecule?If answer is yes,it should be miscible with water,but it doesn't so.Why?

Answer 1

The compound called Ethylenedichloride (EDC or 1,2-dichloroethane) does indeed have two carbon-chlorine bonds. Due to the small difference in electron affinity of these atoms, the dipole moment of the bond is also small.

This is further complicated in that there is a chlorine atom on each "end" so that the dipole moments of each of the Carbon-chlorine bonds are not additive, but partially cancel each other out (when one looks at the whole compound).

Ethylenedichloride is partially soluble in water (about 0.87 g/100 mL at 20° C) due to the dipolar nature of the C-Cl bonds, but it is not miscible like acetone or ethanol, which both can also form Hydrogen bonds with water molecules.

Answer 2

+2

Answer 3

The second poster is correct but it is worth taking some time to explain why ethylene dichloride is not miscible with water even though it is a polar molecule.

There are three forms or isomers of C2H2Cl2, one where the two chlorine atoms are on the same carbon atom and two where the two chlorine atoms are on different carbon atoms. Since the double bond of the ethylene cannot twist, when the two chlorines are on different carbon atoms, you can have a trans- or a cis- form of the dichloride. The cis- form is where the two chlorine atoms are on the same side of the molecule and the trans- form is where they are on opposite sides. All three forms have polar bonds with a carbon atom and a chlorine atom.

The names for the three forms would be 1,1 dichloro ethylene, cis-1,2 dichloro ethylene, and trans- 1,2 dichloro ethylene.

The trans- isomer has the geometry that has two ends that are equally electronegative. Since the chlorine atoms are relatively larger because of additional electron orbitals, they tend to shield the more positive center of the molecule. This in effect nullifies the polar effect and makes the molecule immiscible with water.

There is a similar polar effect with the cis- form and with the form where the two chlorines are on the same carbon atoms. These two forms tend to be more polar than the trans- form and will have a very slight miscibility with water but not enough to mix well with water, which is so much more polar.

Answer 4

Indeed ethylenedichloride is polar.
BUT Miscibility doesnot always depend on polarity of the molecule of the compounds.
Take for example chloroform and water or even you example.

Rather follow the thumb rule:
Organic compounds miscible with Organic compounds
This has fewer exceptions

Answer 5

oil and water don't mix.