i feel like i am wasting my time studying

[batista_123]

for a month and a half now, i have been stuggling with ochem. I have been sitting at the library 7-8 hours a day, memorizing reactions. but then today i read that on the mcat ochem is tested very lightly? i guess that means it is more important to know why something happens, they dont expect you to know WHAT happens?? if thats the way it is, then i will definitely fail.
so i am really confused, i dont know what to do with ochem, i feel like i am studying the wrong thing, or the wrong way.
i want a fresh start. and i am really just frustrated. i dont know what i need to know regarding ochem. for example, the hoffman degradation. if they give me a primdary amide and Br2, do i need to be able to predict the product?
what about all those reactions on EK flashcards?
what about this other reaction? what about that other reaction? what about...?
you know what i mean?
can you help me?

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[Marjan Islam]

Whoa, slow down! Organic Chem. is NOT tested very heavily, and you memorizing complex reactions is NOT the way to go.

Read EK Orgo., paying most of your attention to the first 2 chapters, and the 4th chapter (lab techniques). Know E1, E2, SN1, SN2, and electron withdrawing groups, etc. etc. Not so much reactions. But predict what WOULD happen, using SN1 and SN2, E1 and E2 as guidelines.

Don't fret too much. You'll have 1 Ochem passage, with a few discretes on your mcat. 2 O-chem passages if you're unlucky!

 

[batista_123]

Whoa, slow down! Organic Chem. is NOT tested very heavily, and you memorizing complex reactions is NOT the way to go.

Read EK Orgo., paying most of your attention to the first 2 chapters, and the 4th chapter (lab techniques). Know E1, E2, SN1, SN2, and electron withdrawing groups, etc. etc. Not so much reactions. But predict what WOULD happen, using SN1 and SN2, E1 and E2 as guidelines.

Don't fret too much. You'll have 1 Ochem passage, with a few discretes on your mcat. 2 O-chem passages if you're unlucky!

i have read EK orgo 2 times from cover to cover, and i understand chapters 1,2, and 4 well, but chapter 3 is just a mess, i dont know anything from there because they present many reactions. i have been trying to memorize all the reactions in their flashcards in the back of the book. that is not a good idea?

 

[Forkit]

i have read EK orgo 2 times from cover to cover, and i understand chapters 1,2, and 4 well, but chapter 3 is just a mess, i dont know anything from there because they present many reactions. i have been trying to memorize all the reactions in their flashcards in the back of the book. that is not a good idea?

Supplement EK with Kaplan. I dont think memorizing the reactions will help at all.

 

[carbonfishbone]

i have read EK orgo 2 times from cover to cover, and i understand chapters 1,2, and 4 well, but chapter 3 is just a mess, i dont know anything from there because they present many reactions. i have been trying to memorize all the reactions in their flashcards in the back of the book. that is not a good idea?

Do NOT try to memorize ochem. It will only lead to confusion. Ochem has a very logical reasoning behind what each reaction does. When you understand the basics of ochem thoroughly, the reactions actually begin to makes sense and you can even predict and most importantly reason why it will happen.

I'll be happy to help explain some reactions for you.

 

[batista_123]

Do NOT try to memorize ochem. It will only lead to confusion. Ochem has a very logical reasoning behind what each reaction does. When you understand the basics of ochem thoroughly, the reactions actually begin to makes sense and you can even predict and most importantly reason why it will happen.

I'll be happy to help explain some reactions for you.

it is true that ochem is based on reason and there are a lot of patterns. for example, if C=O is mixed with a nucleophile, the nucleophile attacks the carbon because the carbon has a slight positive charge due to oxygen. I understand the reasons in chapters 1 and 2 of EK. but then chapter 3 shows all these reactions, and i cant find any reasons why these reactions occur or any patterns
there is a lot of reactions for which i predict the wrong product because somewhere in the mechanism something goes wrong and something surprising happens. for example, hoffman degradation. somewhere in there, an R group suddenly jumps from the carbonyl carbon to the nitrogen. how am i supposed to know that unless i memorize it? or the first step of the same reaction, the nitrogen attacks a Br and grabs it for itself. why? why isnt nitogen happy the way it was?
thats just one example, there are a lot of other reactions for which i cannot predict the product because the rules dont work.
usually i can predict the first and second steps, then i get stuck

 

[msd848]

are any of you guys using the BR? I don't know if its worth it considering I only have about a month and a half left..should I stick to EK?

 

[carbonfishbone]

it is true that ochem is based on reason and there are a lot of patterns. for example, if C=O is mixed with a nucleophile, the nucleophile attacks the carbon because the carbon has a slight positive charge due to oxygen. I understand the reasons in chapters 1 and 2 of EK. but then chapter 3 shows all these reactions, and i cant find any reasons why these reactions occur or any patterns
there is a lot of reactions for which i predict the wrong product because somewhere in the mechanism something goes wrong and something surprising happens. for example, hoffman degradation. somewhere in there, an R group suddenly jumps from the carbonyl carbon to the nitrogen. how am i supposed to know that unless i memorize it? or the first step of the same reaction, the nitrogen attacks a Br and grabs it for itself. why? why isnt nitogen happy the way it was?
thats just one example, there are a lot of other reactions for which i cannot predict the product because the rules dont work.
usually i can predict the first and second steps, then i get stuck

Alright, for the first part about Nitrogen attacking Br2. The nitrogen has 2 lone pair so this causes the nitrogen to have have a negative charge, essential turning N into a nucleophile. The Br2 is bound to itself. Br is a highly EN atom, meaning it wants to pull electrons to itself. Thus when N attacks one of the Br (its attacking because its unstable due to having a negative charge. An overall theme in ochem is the charges whether postive or negative are BAD, so atoms/compounds will rearrange so they are neutral), this cause the bond between the two Br's to move onto the other Br. So in a sense, you can think about it as one of the Br's is helping his friend (by bonding with the N) to get more electrons (since its EN atom). This also causes the nitrogen to no longer have a negative charge. So in ochem standards, this is the most logical reaction to occur.

As for how the R changes places, this mechanism/reasoning is not a straight forward. Basically the the O has a negative charge on it, so it will want to collapse to form a more stable carbonyl. When it collapses its going to try to break one of it bonds since C's HATE being bonded to 5 things. So the choices it has to either break a sp3 bond with a C (the R group) or a MUCH more stable sp2 bond (more s character --> more stable) with N. So it is going to break the bond with the R group. However when it breaks this bond this causes the carbon to have a negative charge which makes it unstable so it will immediately attack the N, which causes the Br (a good leaving group) to be kicked off: forming isocyanate.

Oh and a useful tip to know is:

H O N C
1 2 3 4

HONC (pronounced like honk your horn)/1234: This is how many bonds each of the atoms want to be "happy"

 

[batista_123]

Alright, for the first part about Nitrogen attacking Br2. The nitrogen has 2 lone pair so this causes the nitrogen to have have a negative charge, essential turning N into a nucleophile. The Br2 is bound to itself. Br is a highly EN atom, meaning it wants to pull electrons to itself. Thus when N attacks one of the Br (its attacking because its unstable due to having a negative charge. An overall theme in ochem is the charges whether postive or negative are BAD, so atoms/compounds will rearrange so they are neutral), this cause the bond between the two Br's to move onto the other Br. So in a sense, you can think about it as one of the Br's is helping his friend (by bonding with the N) to get more electrons (since its EN atom). This also causes the nitrogen to no longer have a negative charge. So in ochem standards, this is the most logical reaction to occur.

As for how the R changes places, this mechanism/reasoning is not a straight forward. Basically the the O has a negative charge on it, so it will want to collapse to form a more stable carbonyl. When it collapses its going to try to break one of it bonds since C's HATE being bonded to 5 things. So the choices it has to either break a sp3 bond with a C (the R group) or a MUCH more stable sp2 bond (more s character --> more stable) with N. So it is going to break the bond with the R group. However when it breaks this bond this causes the carbon to have a negative charge which makes it unstable so it will immediately attack the N, which causes the Br (a good leaving group) to be kicked off: forming isocyanate.

Oh and a useful tip to know is:

H O N C
1 2 3 4

HONC (pronounced like honk your horn)/1234: This is how many bonds each of the atoms want to be "happy"

thanks so much, 2 things:
1) like i said i like things to be based on reason, i hate memorizing, and i have studied EK and TPR and neither of those explain the way you did, they just say this is what happens, they dont explain why like you did. I wish there was a mcat book that explains things the way you did. or is there? a lot of people like the BR ochem, is that better than EK and TPR?
2)i just want a fresh start. Like i said, i have been memorizing a lot of crap 7 hours a day for the past 45 days and i am just upset because i wasted all that time and the mcat is like a month away and i am scared...soooooo....my plan is to forget the mcat all of this weekend, just rest, do something different, but starting monday i want to study the right way. i need help planning for ochem. what book should i study, any book i study will be presenting a lot of weird reactions, WHAT about the reactions do i have to learn?