Which is the Most Stable?

[RozhonDDS]

I have a simple question:


What is the rank from least to most stable?:
Alkynes
Alkenes
Alkanes
Alcohol
aldehydes
ketones

Also I was wondering the rank of melting points/boling points from least to greatest...
I know it goes alkynes---alkenes---alkanes. But I'm not sure about the aldehydes, ketones, and alcohols.



Thanx evereyone

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[coral2005]

I'm so glad to be done with that stuff. I took the test and forgot everything.

Good luck!

 

[DrTacoElf]

.

 

[kokobean]

Stability (MOST to LEAST)

Alkanes (won't react with much at all)
Alkenes or Alkynes (unsure of which is more stable - if i had to guess I would say alkynes are more stable - i think i remember this is how it was)
Alcohol (reactive but not as much as carbonyl groups if i recall correctly)
Ketone (R groups block carbon to be attacked unlike aldehyde)
Aldehyde (easy attack on carbonyl because just H on one side)

Thats my best shot at it. Not 100% sure really.

i agree.

as for the melting points, alcohols are lower than aldehydes or ketones, because of its hydrogen bonding. Between aldehydes and ketones though, I think it'll be really close - i can't say for sure which one

 

[dat_student]

i agree.

as for the melting points, alcohols are lower than aldehydes or ketones, because of its hydrogen bonding. Between aldehydes and ketones though, I think it'll be really close - i can't say for sure which one

I don't think so. Alcohols have the highest boiling point because of "hydrogen bonding."

off the top of my head:
boiling & melting points:
alcohol > ketone > aldehyde

(635,717)

 

[TXfra]

I don't think so. Alcohols have the highest boiling point because of "hydrogen bonding."

off the top of my head:
boiling & melting points:
alcohol > ketone > aldehyde

(635,717)

To add on to that, dipole dipole interaction in aldehydes and ketones elevate the boiling point. This elevation is less than that in alchols, since no hydrogen bonding is involved. Carboxylic acid however are polar and can form hydrogen bonds. Their boiling points are higher than alcohols.
Alkanes,alkenes, and alkynes are similar in physical properties such that as your increase the chainlength you increase mp bp and density, and if you increase branching you decrease mp bp density. Trans ALKENES has a higher melting point due to symmetry, and Cis ALKENES have a higher boiling point due to polarity. Terminal ALKENES and ALKYNES usually boil at lower temp. than internal ALKENES and ALKYNES.
When comparing bond length however alkanes>Alkenes>alkynes because single bonds are longer.

 

[dat_student]

Stability (MOST to LEAST)

Alkanes (won't react with much at all)
Alkenes or Alkynes (unsure of which is more stable - if i had to guess I would say alkynes are more stable - i think i remember this is how it was)
...

alkynes are less stable than alkenes.

energy required to break a bond:
alkanes > alkenes > alkynes
therefore, reactivity:
alkynes > alkenes > alkanes

combined bond strength:
alkynes > alkenes > alkanes

combined bond length:
alkanes > alkenes > alkynes

(266)