Which has the highest melting/boiling point?

[zibb3r]

alkanes, alkenes or alkanols? and why?

I said alkenes because of the double bond. but im not sure...

[iNerd]

Which has the melting/boiling point?

All substances have a melting/boiling point

EDIT: Haha, I got in before you edited your thread

[Graphite]

When talking mp and bp, we are discussing intermolecular bonding. The strongest form of bond in a small uncharged molecule would be H-bonding. This exists in alkanols.

[Greatness]

Hydrogen bonding is the strongest intermolecular bonding so the alkanol will have the highest melting and boiling point

[zibb3r]

Can you guys please dumb it down for me???

I'm not sure i get it?
 :smitten:

[Greatness]

When a covalent bond is formed, you get intermolecular forces of attraction which are: dipole-dipole bonding, hydrogen bonding and weak dispersion forces. The strength order is hydrogen, dipole-dipole then weak dispersion forces.

[zibb3r]

so does that mean all hydrocarbons with functional groups have higher melting and boiling points?

[Greatness]

Umm i think it would depend on the functional group. But yes.

Hopefully what i told you was right :S i havent done this since unit 1....

[iNerd]

Umm i think it would depend on the functional group. But yes.

Hopefully what i told you was right :S i havent done this since unit 1....

When Unit 1? Defs not AOS1 'cause I can't follow anything this thread is saying...

[pi]

From highest to lowest for hydrocarbons with same number of carbons (eg, pentanol, pentane and pentene): Alcohols (hydrogen bonding between OH groups, and dispersion forces), alkanes (more dispersion forces than alkenes) and then alkenes (least dispersion forces (due to double hydrogen bond).

You can't really compare hydrocarbons with different number of carbons.

[Greatness]

Umm i think it would depend on the functional group. But yes.

Hopefully what i told you was right :S i havent done this since unit 1....

When Unit 1? Defs not AOS1 'cause I can't follow anything this thread is saying...

I cant exaclty remember but im pretty sure we did it late unit 1, couldve been early unit 2.

[pi]

When a covalent bond is formed, you get intermolecular forces of attraction which are: dipole-dipole bonding, hydrogen bonding and weak dispersion forces. The strength order is hydrogen, dipole-dipole then weak dispersion forces.

Also to note, you can get ion-dipole forces too.

[Graphite]

Yes, it is important to note that for intermolecular forces there is no particular ranking in strength. They vary as the size of molecules increase. Therefore we can only say for a particular sized molecule, X bonds are stronger than Y bonds. In general for small charged particles:dispersion<dipole-dipole<H-bonding<ion-dipole<ionic bonding.

So your question can be quite tricky if you get technical with it, for a large alkane, you expect higher mp and bp than a small alkanol molecule. But it is fairly obvious the assumption is the molecules are of the same size when comparing.

You logic to choosing alkene is irrelevant to this question. Yes, double bonds are greater than all bonds present in the other classes of organic molecules however those are intramolecular bonds. When a mixture is boiling it simply means the individual molecules are more distant apart and moving at high speeds not the individual atoms.

[m@tty]

From highest to lowest for hydrocarbons with same number of carbons (eg, pentanol, pentane and pentene): Alcohols (hydrogen bonding between OH groups, and dispersion forces), alkanes (more dispersion forces than alkenes) and then alkenes (least dispersion forces (due to double hydrogen bond).

You can't really compare hydrocarbons with different number of carbons.

Don't call them alcohols.. my teacher said that we had to say alkanols in the new study design.

But I agree with you here, alkanol > alkane > alkene

but it is a really close call between alkanes and alkenes...

see this..

Moderator action: removed real name, sorry for the inconvenience