Any Tips to do well on my O-Chem Exam?

[Harbindoc]

Hey,

I have an O-Chem exam coming up covering Sn1,Sn2, E1, E2, Hydrogenation, Hydroboration, The Bromonium ion reaction (forgot the technical name) the Oxyonium ion reaction and a few others I am sure I am forgetting. My question is: I have done problems, and looked at all the mechanisims involved, but I still don't feel completely ready. Does anyone have any suggestions for doing well on this material? Any "tricks" that worked for you?

Thanks!

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[tryingagain]

I would study.

 

[Dr. Wall$treet]

im pretty nerdy in the fact that i have grown to love ochem, but when iw as learning it, i just wrote out hte reactions a zillion times and whne ur hadn gets sore. Go over them in ur head, like draw them out with the mechanisms in ur head, it is quicker and as effective after u konw ur structures and reagents down, and that always worked for me... that is all ochem isi about. Once u reach ochem 2 ull actually realize and understand of more why things happen and then ull be able to think ur way through more of the reactions rather than memorize purely but it is a must to build a foundation.. good luck

 

[Cerberus]

"My advice to you is to start drinking heavily."
"I'd listen to him - he's pre-med."

 

[14931]

Originally posted by tryingagain
I would study.

i second this

 

[captbadass]

there's studying....and then there's STUDYING ON WEEEEEEEED! i definately suggest this to anybody having trouble with organic chemistry. seriously though, dont stress out. it is true that one bad grade ( meaning anything lower than an A) can mess up your chances for med school. good luck!

CAPTBADASS

 

[TroutBum]

Originally posted by captbadass
there's studying....and then there's STUDYING ON WEEEEEEEED! i definately suggest this to anybody having trouble with organic chemistry. seriously though, dont stress out. it is true that one bad grade ( meaning anything lower than an A) can mess up your chances for med school. good luck!

CAPTBADASS

I'm not sure whether to say or

 

[TroutBum]

Originally posted by captbadass
there's studying....and then there's STUDYING ON WEEEEEEEED! i definately suggest this to anybody having trouble with organic chemistry. seriously though, dont stress out. it is true that one bad grade ( meaning anything lower than an A) can mess up your chances for med school. good luck!

CAPTBADASS

I'm not sure whether to say or

Harbindoc, the one thing that really helped me with SN1, SN2, E1, and E2 was to realize the similarities between SN1 and E1 (it's all about the carbocation) and SN2 and E2 (it's all about the transition state).

I second Wallstreet. The best way to be sure that you know the stuff cold is to be able to draw each mechanism in detail starting with a blank sheet of paper.

Good luck!

 

[Dr Sum Day]

Originally posted by Harbindoc
Hey,

I have an O-Chem exam coming up covering Sn1,Sn2, E1, E2, Hydrogenation, Hydroboration, The Bromonium ion reaction (forgot the technical name) the Oxyonium ion reaction and a few others I am sure I am forgetting. My question is: I have done problems, and looked at all the mechanisims involved, but I still don't feel completely ready. Does anyone have any suggestions for doing well on this material? Any "tricks" that worked for you?

Thanks!

I've always liked using a dry erase board to practice over and over verses wasting tons of paper.

 

[mvervaine]

Originally posted by Harbindoc
Hey,

I have an O-Chem exam coming up covering Sn1,Sn2, E1, E2, Hydrogenation, Hydroboration, The Bromonium ion reaction (forgot the technical name) the Oxyonium ion reaction and a few others I am sure I am forgetting. My question is: I have done problems, and looked at all the mechanisims involved, but I still don't feel completely ready. Does anyone have any suggestions for doing well on this material? Any "tricks" that worked for you?

Thanks!

i always equate Sn1,2, E1,2 reactions with getting hitched or divorced. the 2s only divorce the current partner when a new honey comes along, while as the 1s (weighted down by their steric offspring) are content to do things the traditional way--by divorcing first and then looking.

on second thought, i have no idea what i'm talking about.

 

[deleted9493]

All I do is read through the given examples several times...until I can visualize those examples in my mind. At that point, I'm ready to do the practice problems. Once I've done the practice problems, the mechanisms/concepts typically seem like common sense.
Whatever tricks you end up using to learn this stuff, just make sure that you master these beginning reactions. Sn1, E1, Sn2, and E2...(in addition to the others you mentioned). They are used so often in synthesizing reactions...that you will easily be lost (in the future) if you don't have them down pat. Organic is very much a cumalative learning experience, and I think therein lies much of the difficulty of the course.

 

[LUBDUBB]

HarbinDoc,

I would go to your library, take about an inch thick worth of paper from the copy machine, get one of those liquid pens (so you don't have to press hard to write). Memorize a reaction from your notes and then write the reaction from memory. Do this for all your reactions - I used to write them out about three times each. Then at the end, try writing ALL of your reactions from memory.

I guess this only appies to memorizing reaction mechanisms, which is mostly orgo II. For orgo I (nomenclature and all that), I would grab a few study guides...Shaum's Outlines..etc and just hack out as many problems as you can.

Good luck on your exam !!

~Lubdubb

 

[exigente chica]

Originally posted by TroutBum
I'm not sure whether to say or

Harbindoc, the one thing that really helped me with SN1, SN2, E1, and E2 was to realize the similarities between SN1 and E1 (it's all about the carbocation) and SN2 and E2 (it's all about the transition state).


Good luck!

I also just took this test the other day. U need to remember a couple of things: I make it funny so I can learn it

1. Sn2- likes to hit it from the back
- it depends on <Nu> and <r-X>
-leaving group comes off
-s- likes weak Nu-
- inversion( if chiral)
- Me>1>2>3
2. Sn1
-likes to hit it from both sides
-makes a carbocation
-replace C+ with Nu
- racemic mix
-reanangment
- 3>2>1
3. E1
-all E's like heat (caliente)
- - to a = bond
-they like Strong bases
-bases eat H's
-Beta Anti-coplanar H's -find the c on with the leaving group and go to the next one, that's ur beta carbon, then pick the H that is diagonal from the leaving group
-the H gets eaten
-then the C-H bond pushes and makes a = bond
-u can have a major or minor form (one more substituted is major according to Zateif's rule)

4. E2
- alot like Sn2
-almost sameas above except a Ct
-doesn't have to be B- H's.

Ok, ne other ones, u need help with pm me... I love orgo as u can see

 

[Dr. Wall$treet]

Originally posted by exigente chica
I also just took this test the other day. U need to remember a couple of things: I make it funny so I can learn it

1. Sn2- likes to hit it from the back
- it depends on <Nu> and <r-X>
-leaving group comes off
-s- likes weak Nu-
- inversion( if chiral)
- Me>1>2>3
2. Sn1
-likes to hit it from both sides
-makes a carbocation
-replace C+ with Nu
- racemic mix
-reanangment
- 3>2>1
3. E1
-all E's like heat (caliente)
- - to a = bond
-they like Strong bases
-bases eat H's
-Beta Anti-coplanar H's -find the c on with the leaving group and go to the next one, that's ur beta carbon, then pick the H that is diagonal from the leaving group
-the H gets eaten
-then the C-H bond pushes and makes a = bond
-u can have a major or minor form (one more substituted is major according to Zateif's rule)

4. E2
- alot like Sn2
-almost sameas above except a Ct
-doesn't have to be B- H's.

Ok, ne other ones, u need help with pm me... I love orgo as u can see

Um that is wrong for E1-they do not like strong bases, rather weak bases are favored. E2 uses strong bases.. Both E1 and E2 are favored over SN1 and SN2 when dealing with a bulky base/nucleophile due to the fact that E rxns do not attack and tehrefore bulky bases do not interfere with the rxn.. but anyway E1 is NOT strong bases.. that is E2

 

[Gleevec]

E1 can be strong or weak base, doesnt matter since the carbocation intermediate is so unstable.

 

[Dr. Wall$treet]

Sorry ur right, i was just trying to say that it was E2 where a strong base required.. and E1 can have a weak.. but yes doenst matter.

 

[deleted9493]

Actually it does matter. A strong base (like an alkoxide) will certainly incite E2 over E1. In primary and secondary carbons...there's obviously competition with Sn2. But with tertiary carbons, the energy of activation for E2 in the presence of a strong base is much less than E1. This difference in activation energy is due to the reluctance of the leaving group to leave independently in E1(slow step).

 

[vivekap2007]

I would treat it like a math class by learning hte theorems (Sn1,2 etc) then practice applying them to rxns you haven't seen before. I didn't memorize mechanisms cause i thought it was easier to work them out, same for rxns.

 

[Gleevec]

Originally posted by hudsontc
Actually it does matter. A strong base (like an alkoxide) will certainly incite E2 over E1. In primary and secondary carbons...there's obviously competition with Sn2. But with tertiary carbons, the energy of activation for E2 in the presence of a strong base is much less than E1. This difference in activation energy is due to the reluctance of the leaving group to leave independently in E1(slow step).

A strong base doesnt incite E1, "incite" refers to the rate determining step. The carbocation intermediate is formed in this step already, and elimination can take place via E1 with strong or weak base.

What determines E1 or E2 is whether you formed that carbocation or not, and whether it is bulky (the competition you refer to)

So for E1 in general you use weak bases, but you can you use strong bulky bases as well. For E2 you have to use the strong base since that base has to facilitate the reaction. E1 easier since its already a carbocation.

 

[Dr. Wall$treet]

Originally posted by Gleevec
A strong base doesnt incite E1, "incite" refers to the rate determining step. The carbocation intermediate is formed in this step already, and elimination can take place via E1 with strong or weak base.

What determines E1 or E2 is whether you formed that carbocation or not, and whether it is bulky (the competition you refer to)

So for E1 in general you use weak bases, but you can you use strong bulky bases as well. For E2 you have to use the strong base since that base has to facilitate the reaction. E1 easier since its already a carbocation.

Ok glee, i was going to leave this one but as i suspected ur that type of jerkoff who has to try to prove someoen wrong or be right, exctl why i said id wiep u out in medschool, grade wish, and all other ways. anyway u wanna go ochem with me ill stomp ya in that.
Actually if a carbocation is formed it does matter because once the cation is formed the stability of the transition state, is dependant on the solvation and stabilizatoin of that cation, and taht is acomplished via a protic solvent. now u cannot use a protic solven effectively with a strong base or u wotn have a strong base anymore! which means when a cation is formed.. an E1 rxn, the weak base will always go before a strong base due to its superior ability to stabalize the cation. Now talkign tertiary or benyzlic/allylic its pretty stable as is, so no solvation is needed and yes a strong base will work Bulkiness has nothign to do with E1 v. E2, as the mechanism is no differnet in terms of steric hindrince...

try not having to be right all the time and lighten up ya dumbfuk, and yes ******* like u who care about a life of grades.. ill come in, not study and set the curve and knock ur ass down to reality.. i will win over u in every way u wanna be smartass ltrs

 

[UCLA2000]

...study

 

[phil413ru]

I am a big OChem nerd, and a very visual learner. What I did, was make visual analogies. Most of you will think this is dorky, but those I have tutored have always laughed, but then said they get it.
I will use nucleophilic attack on methyl-halogen as ex. --picture the SN2 as a little old lady walking 3 small poodles (hydrogen) and a big irish wolfhound (halogen). The poodles are very close to the lady, so she can hold a very short leash with them and be able to control them. (the strong covalent bond btw carbon and hydrogen). However, the Irish wolfhound is too big to have a very short leash. In order to control the dog, the lady must have a longer leash (longer bond). The dog is very strong and tells to pull lady forward (electronegativity and good leaving group character of halogen). If the lady is not careful the dog will pull away (good leaving group). If the lady is walking in a bad neighborhood like a dark neighboorhood alley way in NYC, she has a greater likelihood of being attacked (SN2 characteristic Aprotic solvent).
Well, one night, the lady is walking her four dogs when someone with a very negative attitude comes up to the lady from behind (nucleophile). The lady is so started that she loses control of the wolfhound--the dog takes off running, leaving the lady, attacker and 3 poodles behind. The poodles are so tightly held by lady that they cannot run away, but do run to front --opposite side of attacker. (inversion of configuration).

Anyway, I have lots of analogies like this for SN2, E1, E2. If you don't already think I am completely crazy, email/PM me and I can give more.
For those of you who are O-chem geniuses, I know this is "oversimplifying" but it makes an easy to remember strategy because the mind works thinks in pictures. It has worked with some that I tutor, and it make learning fun. I know it may be stupid, but I love it!
Do whichever way works for you--hard memorization of diagrams, or fun analogies.

(Hence, I used to want to be fiction writer before going into health/science field)

Good luck!!

 

[exigente chica]

Originally posted by Dr. Wall$treet
Ok glee, i was going to leave this one but as i suspected ur that type of jerkoff who has to try to prove someoen wrong or be right,

Seems like u were doing the same thing to me....

 

[Dr. Wall$treet]

Originally posted by exigente chica
Seems like u were doing the same thing to me....

Dumb Biitch

 

[Cerberus]

Originally posted by Dr. Wall$treet
Dumb Biitch

God you are a assclown.

 

[Continuum37]

Originally posted by Dr. Wall$treet
Ok glee, i was going to leave this one but as i suspected ur that type of jerkoff who has to try to prove someoen wrong or be right, exctl why i said id wiep u out in medschool, grade wish, and all other ways. anyway u wanna go ochem with me ill stomp ya in that.
Actually if a carbocation is formed it does matter because once the cation is formed the stability of the transition state, is dependant on the solvation and stabilizatoin of that cation, and taht is acomplished via a protic solvent. now u cannot use a protic solven effectively with a strong base or u wotn have a strong base anymore! which means when a cation is formed.. an E1 rxn, the weak base will always go before a strong base due to its superior ability to stabalize the cation. Now talkign tertiary or benyzlic/allylic its pretty stable as is, so no solvation is needed and yes a strong base will work Bulkiness has nothign to do with E1 v. E2, as the mechanism is no differnet in terms of steric hindrince...

try not having to be right all the time and lighten up ya dumbfuk, and yes ******* like u who care about a life of grades.. ill come in, not study and set the curve and knock ur ass down to reality.. i will win over u in every way u wanna be smartass ltrs

Besides being an assclown, it's hard to take anyone's organic explanations seriously when it's almost impossible to read the response due to the spelling and grammar.

 

[exigente chica]

Originally posted by Dr. Wall$treet
Dumb Biitch

This dum girl is getting a A in orgo, loser...I really hope I don't see you in med school, poor patients

 

[osar92]

I agree..... the best way to do well on an organic exam is to write out all the reactions a million times... thats the easiest way to memorize them all
To not waste so much paper, i use one of those little dry erase marker boards