OChem...help me i becoming stupider...

[future_dentist]

---

Members do not see this ad.

Which of the following statement is right....

I read it somewhere and made a note of this:

trans has a higher melting point due to its symmetry...
cis has a higher boiling point due to its polarity...

I was just reviewing some questions #80 Kaplan (Full test-Before the test day) and noticed the correct statement says:

Q: Which of the following statement is true regarding melting pt and boiling pt of cis and trans 1,2-dichloroethane:

Ans: (D) the melting and boiling points of cis isomer are higher....

which kind of make sense cause high boiling point=high melting pt. right??

 

[Envision]

Which of the following statement is right....

I read it somewhere and made a note of this:

trans has a higher melting point due to its symmetry...
cis has a higher boiling point due to its polarity...

I was just reviewing some questions #80 Kaplan (Full test-Before the test day) and noticed the correct statement says:

Q: Which of the following statement is true regarding melting pt and boiling pt of cis and trans 1,2-dichloroethane:

Ans: (D) the melting and boiling points of cis isomer are higher....

which kind of make sense cause high boiling point=high melting pt. right??

no, higher boiling pt does not equal higher melting pt. stick to the first definition. for 1,2 dichloroethane is cis formation, that means it has a dipole (the Cl are both oriented in one direction creating a polarity), and this polarity will give it a higher boiling pt comparing to a trans 1,2 dichloroethane (Cl groups cancel out, no polarity). however, the trans formation has a higher melting pt because it can easily pack itself together tightlier than its cis isomer, giving it a higher melting pt.