who knows O-chem? :D

[phissionkorps]

I'd look it up in my book, but I finished the class and sold the book. Trying to study some O-chem for the MCAT, so uhh....

During dehydration of 1° and 2° alcohols, does the 1,2 methyl shift always occur if possible?

Also, is it even called a 1,2 methyl shift?
Is there a 1,3 methyl shift? Or is that a 1,3 hydride shift? If hydride, when does that occur?

Thanks in advance to whoever studies this science from hell.

 

[jm82792]

I love science but man that looks non interesting and hard
I hope for the best and go here for help he has been around for years and should help : http://scitoys.com/cgi-bin/board/discus.cgi
the guy works for google and he is a sci weiz in math whatever he should know it hope he helps

 

[joossa]

this science from hell.

LOL! Understatement? I’ll have to pass, chem is not my subject… Thank goodness Organic isn’t a requirement for my Bio Minor.

Good luck on your MCAT, BTW.

 

[nepenthes_ak]

Oh god I hope I don't have to take Organic Chemistry for a bio Major! I barley passed Chemistry!

 

[Presto]

The only thing I remember on that subject (and not very well...anyone feel free to correct me) is the molecule will always spend as much time as possible in its most stable form. However, it will still spontaneously shift to higher energy forms every now and then...and then shift back. So yeah, since the methyl shift makes it more stable, it will shift to that form.

I don't think shifts "hop" over atoms in the molecule...so thus I don't think 1,3 shifts happen...again, don't take my word for it.

That's all I've got. I share the sentiment.

nep ak, unfortunately you probably will have to take it...

 

[wmgorum]

Sorry... I didn't have to take a chemistry class to finish up either of my degrees... oh, the joys of majoring in American Sign Language...

 

[phissionkorps]

If you guys are going to be Bio majors, you'll probably have to take inorganic 1 and 2, and organic 1 and 2.

I would've taken them anyway to prepare for the MCAT, but my school makes you take them as "adjunct requirements".

 

[Ozzy]

 

[herenorthere]

Just remember boys and girls, there tends to be quite a bit of correlation between the difficulty of your college classes and the quality of your starting pay and job prospects. So if you're looking to major in something like biology and can do it with or without organic, take the organic. Suffering through a couple semesters of pain tends to be rewarded in the end. It can be the difference between sifting through graduate assistantship & job offers or asking, "do you want fries with that?" As for phissionkorps' actual question; I have no idea. My degree attempted to crush our spirits with different classes.

 

[vraev]

ooh..I freakin hate orgo. hmm...from what I remember, methyl shifts are very rare. Consider this...hydride shifts occur only once in a while.....so methyl shifts are pretty unfavourable. Hydride shifts are when there is a way such that a tertiary carbocation that can be formed, the hydride from the tertiary carbon is "transferred" to the primary site of carbocation formation. Methyl shifts CAN occur as well in cases where there are rings involved and the tertiary carbon doesn't have a H and instead a methyl group lying around. lol!

This above info can be "right" OR... I am in big freakin trouble.. lol! that means tons to study for my exam.

 

[phissionkorps]

I finally figured it out...took forever, but I found it.

First of all, its called a 1,2 methide shift, not methyl as I previously thought.
And, in terms of 1° and 2° alcohol dehydrations, if possible it WILL occur, and its possible either always or 99% of the time.
Theres no 1,3 methide or 1,3 hydride shift, but there is a 1,2 hydride shift.
"Molecular rearrangements of this type frequently accompany Sn1 reactions, especially in highly ionizing, non-nucleophilic solvents such as formic acid and acetic acid. As a rule of thumb, rearrangements will occur whenever they can produce carbocations of equal or greater stability"
(taken from: http://www.usm.maine.edu/~newton/Chy251_253/Lectures/Carbocations/default.html)

Looks like you and I both need to brush up on the O-chem.
PS: chemistry kills my inner child

 

[herenorthere]

Oh, you meant methide shift. Well of course there's no 1,3 methide or 1,3 hydride shift, but there is a 1,2 hydride shift. As is taught in every kindergarten, molecular rearrangements of this type frequently accompany Sn1 reactions, especially in highly ionizing, non-nucleophilic solvents such as formic acid and acetic acid. As a rule of thumb, rearrangements will occur whenever they can produce carbocations of equal or greater stability. Looks like some kids snuck out for extra milk & cookies the day this subject was covered.

 

[Clint]

The name methide refers to the H3C:- group; in other words, a methyl anion. While 1,2-shifts of other alkyl groups can occur, 1,2-methide shifts are the most common. Another group that undergoes frequent rearrangement is a phenyl ring.

Damn kids and your cookies I bet you didn't even know that in the methyl cation, the orbitals bonding the three hydrogen atoms to the central carbon are all orthogonal to the vacant p orbital on that sp2 hybridized carbon.


*Snort*

 

[PlantAKiss]

Looks like some kids snuck out for extra milk & cookies

My teachers would have rapped my knuckles if I'd said "snuck." Maybe its finally been added to the dictionary like "ginormous" and "suduko". I wonder if they've added "geocaching" yet.

 

[herenorthere]

Irregardless of what you think, snuck is a word. After all, it has 2,730,000 hits in Google, so it must be proper English. No one questions the legitimacy of antidisestablishmentarianism, yet it only has 118,000. Snuck even has more hits than "Scooter Libby", which comes in with a mere 2,220,000. Geocaching has a whopping 6,500,000, but who'd expect anything less for a geek activity like that?