Organic Chemistry Halp

tedkennedy · 01-27-2010, 09:47 AM

I know some of you guys are organic chem wizards.

I am taking orgo2 and it is moving extremely fast and I took orgo1 2 years ago and i remember nothing.

I am probably going to look into getting a tutor or some other form of help but right now I have a quiz due tonight that I am totally clueless about and i wont be able to find any help that fast (the class only started 3 days ago and they did not teach what is on the quiz)

Can anyone help me figure out some pretty basic synthesis but more importantly explain step by step the thought process that goes into the answer?

Here is the first question:

Predict the major Br monosubstituion product of this reaction.

Captain Cannabis · 01-27-2010, 10:16 AM

i don't see a reaction

Br synthesis major products is whatever side of the bond is less substituted. unless selective reagents are used (ie: LiBr vs Cu2Br). Br is big, polarizable and fuzzy.

i hope this helps

edit: also this is assuming you are using 1equivalent of bromine

tedkennedy · 01-27-2010, 10:40 AM

Quote:

Originally Posted by Captain Cannabis

i don't see a reaction

Br synthesis major products is whatever side of the bond is less substituted. unless selective reagents are used (ie: LiBr vs Cu2Br). Br is big, polarizable and fuzzy.

i hope this helps

edit: also this is assuming you are using 1equivalent of bromine

hmmm thats wierd the picture was showing up for me when i first posted it, ah i think its because i closed the website which the quiz is temporarily hosted on... this should work

first off what do you mean by "substituted"?

the next question is the same except with this reaction

how is this different and why

Captain Cannabis · 01-27-2010, 10:43 AM

https := secure http

passwords etc. take a screenshot or just describe it with words

tedkennedy · 01-27-2010, 11:00 AM

can you still not see thie pictures? ok ill take a screenshot, BRB

Captain Cannabis · 01-27-2010, 11:02 AM

my license for chemdraw expired. weakass paint drawings will follow while i try and renew it

tedkennedy · 01-27-2010, 11:03 AM

try marvinsketch, its what we use in my class and i think its free , also thanks much in advance you are greatly helping me

the drawing dont even need to be that good nor do you need to spend time drawing it, if you can explain using words that can also help me. i have a textbook next to me that i am skimming through i just honestly dont know where to start.

Captain Cannabis · 01-27-2010, 11:11 AM

the first rxn favours allylic substitution because of the resonance stability of the intermediate. draw mechanism if you need to understand this better. it is a free radical chain rxn with 3 steps. the intermediate is favoured because the charge is displaced through the ring ONLY when Br is in that one spot.
edit: the minor product of this reaction is a disubstitution at the same carbon atom

the second reaction favours the substitution on the end of the molecule due mostly to steric hinderance. stereochemical control of this reaction can be acheived with low temperatures 1equivalent of Br in reasonable yeild.

tedkennedy · 01-27-2010, 11:15 AM

Awesome, that helped me alot... I will inevitably have more questions but i have to ponder my book for a while

by the way how do you go about naming a hexane with 3 double bonds and an ethyl group?

Captain Cannabis · 01-27-2010, 11:19 AM

same way you name anything

find the longest chain and then start at the end with the biggest (heaviest) groups.

so a hexane with an ethyl group can take names like this:
2-ethyl-hexa-1,3,5-ene

i tried to draw a picture but without chemdraw its a waste of time

tedkennedy · 01-27-2010, 11:24 AM

ah ok you just locate the double bonds and add an -ene ending. i see

Predict the major Br monosubstituion product of this reaction.

in this one would the Br go next to the double bond (the 3rd carbon) for the same reason as the first problem? What does NBS stand for?

Captain Cannabis · 01-27-2010, 11:27 AM

you have to be careful when you have an ethyl near the end because it can make a good 7carbon chain and your most-technically-correct name becomes something stupid like septa-2,4,6-ene or something

naming is stupid

tedkennedy · 01-27-2010, 01:36 PM

what does it mean "substituted groups"?

Captain Cannabis · 01-27-2010, 02:29 PM

NBS is nbromosuccinimide. It easily and affordably adds one mol eqv of bromine. You are right (sort of) that it will substitute on the 3 carbon as a MAJOR product(because of the allylic stability). Keep in mind there will be trace amounts of 1 substituted monobrominated products as well that need to be removed via purification.

421 · 01-27-2010, 03:39 PM

wat

Captain Cannabis · 01-27-2010, 04:04 PM

come on keep up, this is basic stuff

BigSpliffSmoka · 01-28-2010, 05:43 AM

shit... which one of you can I pay to take the finite math i've been putting off for the past 3 years

sweet_leaf · 01-28-2010, 08:20 AM

Quote:

Originally Posted by Captain Cannabis

you have to be careful when you have an ethyl near the end because it can make a good 7carbon chain and your most-technically-correct name becomes something stupid like septa-2,4,6-ene or something

naming is stupid

Blame those IUPAC fuddy duddies

01-27-2010, 09:47 AM	#1 (permalink)
tedkennedy now 14% blacker Join Date: Apr 2005 Posts: 3,229 Thanks: 71 Thanked 585 Times in 364 Posts	Organic Chemistry Halp I know some of you guys are organic chem wizards. I am taking orgo2 and it is moving extremely fast and I took orgo1 2 years ago and i remember nothing. I am probably going to look into getting a tutor or some other form of help but right now I have a quiz due tonight that I am totally clueless about and i wont be able to find any help that fast (the class only started 3 days ago and they did not teach what is on the quiz) Can anyone help me figure out some pretty basic synthesis but more importantly explain step by step the thought process that goes into the answer? Here is the first question: Predict the major Br monosubstituion product of this reaction. __________________ matthew munari Last edited by tedkennedy; 01-27-2010 at 10:01 AM.

01-27-2010, 10:16 AM	#2 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	i don't see a reaction Br synthesis major products is whatever side of the bond is less substituted. unless selective reagents are used (ie: LiBr vs Cu2Br). Br is big, polarizable and fuzzy. i hope this helps edit: also this is assuming you are using 1equivalent of bromine __________________ fuck the monkeys Last edited by Captain Cannabis; 01-27-2010 at 10:21 AM.

01-27-2010, 10:43 AM	#4 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	https := secure http passwords etc. take a screenshot or just describe it with words __________________ fuck the monkeys

01-27-2010, 11:00 AM	#5 (permalink)
tedkennedy now 14% blacker Join Date: Apr 2005 Posts: 3,229 Thanks: 71 Thanked 585 Times in 364 Posts	can you still not see thie pictures? ok ill take a screenshot, BRB __________________ matthew munari

01-27-2010, 11:02 AM	#6 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	my license for chemdraw expired. weakass paint drawings will follow while i try and renew it __________________ fuck the monkeys

01-27-2010, 11:03 AM	#7 (permalink)
tedkennedy now 14% blacker Join Date: Apr 2005 Posts: 3,229 Thanks: 71 Thanked 585 Times in 364 Posts	try marvinsketch, its what we use in my class and i think its free , also thanks much in advance you are greatly helping me the drawing dont even need to be that good nor do you need to spend time drawing it, if you can explain using words that can also help me. i have a textbook next to me that i am skimming through i just honestly dont know where to start. __________________ matthew munari Last edited by tedkennedy; 01-27-2010 at 11:08 AM.

01-27-2010, 11:11 AM	#8 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	the first rxn favours allylic substitution because of the resonance stability of the intermediate. draw mechanism if you need to understand this better. it is a free radical chain rxn with 3 steps. the intermediate is favoured because the charge is displaced through the ring ONLY when Br is in that one spot. edit: the minor product of this reaction is a disubstitution at the same carbon atom the second reaction favours the substitution on the end of the molecule due mostly to steric hinderance. stereochemical control of this reaction can be acheived with low temperatures 1equivalent of Br in reasonable yeild. __________________ fuck the monkeys

01-27-2010, 11:15 AM	#9 (permalink)
tedkennedy now 14% blacker Join Date: Apr 2005 Posts: 3,229 Thanks: 71 Thanked 585 Times in 364 Posts	Awesome, that helped me alot... I will inevitably have more questions but i have to ponder my book for a while by the way how do you go about naming a hexane with 3 double bonds and an ethyl group? __________________ matthew munari

01-27-2010, 11:19 AM	#10 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	same way you name anything find the longest chain and then start at the end with the biggest (heaviest) groups. so a hexane with an ethyl group can take names like this: 2-ethyl-hexa-1,3,5-ene i tried to draw a picture but without chemdraw its a waste of time __________________ fuck the monkeys

01-27-2010, 11:24 AM	#11 (permalink)
tedkennedy now 14% blacker Join Date: Apr 2005 Posts: 3,229 Thanks: 71 Thanked 585 Times in 364 Posts	ah ok you just locate the double bonds and add an -ene ending. i see Predict the major Br monosubstituion product of this reaction. in this one would the Br go next to the double bond (the 3rd carbon) for the same reason as the first problem? What does NBS stand for? __________________ matthew munari Last edited by tedkennedy; 01-27-2010 at 11:27 AM.

01-27-2010, 11:27 AM	#12 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	you have to be careful when you have an ethyl near the end because it can make a good 7carbon chain and your most-technically-correct name becomes something stupid like septa-2,4,6-ene or something naming is stupid __________________ fuck the monkeys

01-27-2010, 01:36 PM	#13 (permalink)
tedkennedy now 14% blacker Join Date: Apr 2005 Posts: 3,229 Thanks: 71 Thanked 585 Times in 364 Posts	what does it mean "substituted groups"? __________________ matthew munari

01-27-2010, 02:29 PM	#14 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	NBS is nbromosuccinimide. It easily and affordably adds one mol eqv of bromine. You are right (sort of) that it will substitute on the 3 carbon as a MAJOR product(because of the allylic stability). Keep in mind there will be trace amounts of 1 substituted monobrominated products as well that need to be removed via purification. __________________ fuck the monkeys

01-27-2010, 03:39 PM	#15 (permalink)
421 Alice D. Millionaire Join Date: Aug 2004 Location: Appalachia Posts: 1,780 Thanks: 448 Thanked 106 Times in 69 Posts	wat __________________ further forward

01-27-2010, 04:04 PM	#16 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	come on keep up, this is basic stuff __________________ fuck the monkeys

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01-28-2010, 05:43 AM	#17 (permalink)
BigSpliffSmoka ...@ War, BRB Join Date: Oct 2002 Location: Chicago Posts: 967 Thanks: 16 Thanked 54 Times in 41 Posts	shit... which one of you can I pay to take the finite math i've been putting off for the past 3 years __________________ So if the devil wear Prada, Adam Eve wear Nada, I'm in between, but way more fresher.

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