Question

There are three different dichloroethylenes (molecular formula C2H2Cl2), which we can designate X, Y, and Z. Compound X has no dipole moment, but compound Z does. Compounds X and Z each combine with hydrogen to give the same product: C2H2Cl2(X or Z) + H2 → ClCH2―CH2Cl What are the structures of X, Y, and Z? Be sure to include lone pair electrons. X draw structure ... Y draw structure ... Z draw structure ...

Answer 1

Explanation:

The three options are:

1) Both Cl in the same carbon

2) One Cl in each C and both in the same side of the double bond (cis )

2) One Cl in each C and both in the oposite sides of the double bond (trans )

Options 2 and 3 are geometrical isomers and will generate the same products, so this options will be X and Z. Therefore Y is the one described in option 1.

Now, having the two electronegative atoms (Cl) in the same side will create a dipole moment but if they are oposed, the dipole moment will be canceled. Being that said we can affirm that the option 2) is Z and the option 3) is X

In the figure you can see the structures of X, Y and Z from top to bottom.

Answer 2

Answer:

Compound X= (E)-1,2-dichloroethene

Compound Y= 1,1-dichloroethene

Compound Z= (Z)-1,2-dichloroethene

Explanation:

In this case we will have 3 isomers which have the same formula. If we use the formula, the options we have are that the chlorides are attached to the same carbon (compound Y) or different carbons (Compounds X and Y).

Now, the problem gives a clue about compounds X and Y, hydrogenation results in the same compound (see figure) therefore the only difference between the compounds is the orientation of the Cl groups, therefore one of them it must be "E" and the other "Z" (this nomenclature should be used for alkenes, since the cis / trans nomenclature is used for other types of molecules), so the question is which is the cis isomer and which is the Isomer Z ?

The problem says that compound X has no dipole moment, therefore in compound X the Cl groups must have opposite directions such that the dipole moments of both cancel each other out. In conclusion, compound X is the isomer E, compound Y is the compound in which the Cl groups are on the same carbon and compound z is the isomer Z.