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Capers
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Organic Chemistry Homework Conundrum
#18903989 - 09/28/13 06:44 PM (10 years, 4 months ago) |
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I have spent hours and hours on this assignment. I have answered 43 of 48 questions correctly but I'm stuck on the last five. Could someone please help me?
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Chowder963
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18904316 - 09/28/13 08:12 PM (10 years, 4 months ago) |
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Wish I could help but no, 7k posts once you reply to this.
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Ganzig
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Re: Organic Chemistry Homework Conundrum [Re: Chowder963]
#18904451 - 09/28/13 08:39 PM (10 years, 4 months ago) |
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Got my recently graduated chem master buddy on it.
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Ganzig
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Re: Organic Chemistry Homework Conundrum [Re: Ganzig]
#18904522 - 09/28/13 08:57 PM (10 years, 4 months ago) |
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Buddy left his ochem book at work. He says he needs it to figure it out.
Sorry bud. Good luck.
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Ganzig
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Re: Organic Chemistry Homework Conundrum [Re: Ganzig]
#18904547 - 09/28/13 09:05 PM (10 years, 4 months ago) |
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He said
"Look at the reagents, the final product after treatment and if they can't figure it out, google "mass-charge peaks of 67. It's a 4-5 carbon aliphatic chain with a single functional group. Tell your homie to open their textbook."
That is all I got from him.
Cheers.
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Ganzig]
#18905721 - 09/29/13 03:26 AM (10 years, 4 months ago) |
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EDIT: its probably an isomer of cyclopentene, I'm working on the 3-methylcyclobutene possibility.
Edited by mellowparty (09/29/13 05:06 AM)
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Ganzig]
#18905838 - 09/29/13 04:52 AM (10 years, 4 months ago) |
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Last time I studied chemistry was in highschool years ago but it was university-level chemistry and I did put a lot of effort into learning everything I could (I hope I still remember something). This is my solution to the problem and I'd suggest you run it by the answer book or by a real chemist to verify my ramblings 
Anyway the bromine decoloration would indicate a double (maybe triple) bond. The electron impact mass spec data tells us the mass of the compound to be around 67 (cause that would be the peak of the predominant ionized species).
Osmium tetraoxide reacts with alkenes in a [3+2] cycloaddition yielding an intermediate osmate ester that breaks down to a vicinal cis-diol. Periodic acid acts on the vicinal diols to break the bond between the two carbons from the functional (and now oxidized) group thus forming two aldehyde groups which are oxidized to 2 carboxylic groups by silver oxide. And its says the dicarboxylic acid has enantiomers. If it takes 13.7 ml 0.1 M NaOH to neutralize a dicarboxylic acid (B) then in 100 mg of B there are slighly more moles of B than there are hydoxyl moles in half the specified amount of base (cause its a dicarboxylic acid). In other words in 100 mg of B there must be slightly over than 685 µmoles which in turn can help you get an estimate of the molecular mass of A and knowing that 30% of the protons have a δ 1.8-2.2 chemical shift you can start to build a picture of what A might look like (with the fact that B is an enantiomer helping you select the isomer that is A). Given that the phosphoryl chloride treatment yields a cyclic anhydride I believe A is a cyclic compound.
IMHO we are talking about 3-methylcyclobutene and methylsuccinic acid (A and B resp.).
Someone please check if I made a mistake somewhere.
Edited by mellowparty (09/29/13 05:06 AM)
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18906302 - 09/29/13 09:14 AM (10 years, 4 months ago) |
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Quote:
zappateer said: I have spent hours and hours on this assignment. I have answered 43 of 48 questions correctly but I'm stuck on the last five. Could someone please help me?

I just realized the blank spaces are for the chemical structures.
 A
 B
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18907517 - 09/29/13 03:10 PM (10 years, 3 months ago) |
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Post more problems, OP! I'm bored.
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Capers
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Re: Organic Chemistry Homework Conundrum [Re: mellowparty]
#18910224 - 09/30/13 07:28 AM (10 years, 3 months ago) |
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You did not get this one correct, however you were close. Here is the actual solution:

I really appreciate all your help. +5 shrooms for you! I don't have any more conundrums presently but I will once I start my next homework assignment. This time I will post my questions further from the due date so we have time to figure them out.
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18910232 - 09/30/13 07:31 AM (10 years, 3 months ago) |
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Could you explain to me the EI mass spec data. How did 3-methylcyclopentene gives a peak of 67?
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Capers
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Re: Organic Chemistry Homework Conundrum [Re: mellowparty]
#18910238 - 09/30/13 07:34 AM (10 years, 3 months ago) |
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You must be thinking of the molecular ion peak. They were talking about the base peak, which is the fragment that occurs with the most prevalence, I believe. The molecular ion peak corresponds to the molecule's actual weight.
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18910245 - 09/30/13 07:35 AM (10 years, 3 months ago) |
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Fair enough, that was a wild guess on my part. I should've used the neutralization data to get a better estimate of its molecular mass (is that how its done?).
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Capers
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Re: Organic Chemistry Homework Conundrum [Re: mellowparty]
#18910287 - 09/30/13 07:53 AM (10 years, 3 months ago) |
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I really don't know. Most of our homework problems are unique. I don't remember seeing anything like this in class. I think the neutralization data was for figuring out Compound B's weight. This makes sense because Compound B weighs 146 g, which is double the number I got from the neutralization data. If it took .0137 L of .1 M NaOH to neutralize .1 g of Compound B, then Compound B's molecular weight should have been 73 g, as I saw it at the time:
.0137 L * (.1 moles/ 1 L) = .00137 moles NaOH.
.00137 moles NaOH are required to neutralize .1 g of Compound B.
molecular weight = grams / mole = .1 g/.00137 moles = 73 grams
Since 73 is half of 146, it must take one mole of NaOH to neutralize two moles of Compound B.
Sorry if this was a slopppy explanation. I don't really get it myself and I have class in a few minutes.
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18910340 - 09/30/13 08:11 AM (10 years, 3 months ago) |
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This one is pretty interesting.
How does the EI base peak give us useful information? That number 67 made me believe it was 3-methylcyclobutene we're talking about (which is actually 68). I need to do more reading on mass spec stuff.
EDIT: I saw your response in the middle of writing my calculations.
It says dicarboxylic acid so I'd imagine it takes 2 moles of NaOH to neutralize every mole of the dicarboxylic acid. But the moles equal the concentration times volume so n(NaOH)=0.1M x 0.0137 l = 0.00137 moles
But thats 2x the moles of the dicarboxylic acid so n(acid)=0.00137/2=0.000685 moles
And if the moles are equal to n=m/M therefore M=m/n=0.1/0.000685=146 g.mol-1 for the dicarboxylic acid
Its formula is C6H10O4=6x12+10x1+4x16=146 g.mol-1 so yeah its the same thing
Damn n***a I should pay more attention to the neutralization data cause I'm one methylene group short of success 
Fun stuff tho, definitely post your next assignment.
Edited by mellowparty (09/30/13 08:13 AM)
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Capers
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Re: Organic Chemistry Homework Conundrum [Re: mellowparty]
#18911683 - 09/30/13 03:05 PM (10 years, 3 months ago) |
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Quote:
mellowparty said:
It says dicarboxylic acid so I'd imagine it takes 2 moles of NaOH to neutralize every mole of the dicarboxylic acid.
Ah, good point. That explains why the moles were doubled.
Quote:
mellowparty said: Fun stuff tho, definitely post your next assignment.
Will do. So, I'm just curious. How is it that you know how to do these problems? What was your field of study?
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drkkenny
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18911786 - 09/30/13 03:29 PM (10 years, 3 months ago) |
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My teacher introduced this assignment to our class last Fall, it was after we had been introduced into a new math program, which I had taken last year but had failed. They kicked me out of the school and banned me from ever participating in class again, and instead of using me as there example of excellence they used someone else far more reliable, someone that seemed a sort of prodigy compared to the less gifted students. Now because my mother also was recently transferred to the history department of that same school I decided to switch into that class, where she freely gave me hints about the assignment we were working on, and which gave me an upper edge against others in my class. Noone suspected that during the class that the person teaching was my mother, I told all the students that she was a friend of my mothers substituting for her for a short session. Though I discovered that someone in the class found out that she was my mom, and so after school they came to my house and asked me why I hadn't mentioned it before, but, my girlfriend being on the other line couldn't speak to him. His friend also came over a day after he did but we didn't talk for long before my other friend came and I had to get rid of him, and so even though he followed us around we never acknowledged his presence, he never seemed to even be in the conversation so in some ways he felt offended, but in a way that didn't seem to imply that we were doing it purposely and that he hadn't taken it hard.
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mellowparty
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Re: Organic Chemistry Homework Conundrum [Re: Capers]
#18911815 - 09/30/13 03:34 PM (10 years, 3 months ago) |
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My field is molecular biology and although I haven't studied chemistry at university I love it.
In high school we did a lot of chemistry including undergrad material. My favourite parts were heterocycles and stereochemistry preferably combined. As for the problems I do a lot of reading and learn a long the way. And I get a kick out of solving it (which I failed on this occasion ).
The teacher once said something about LSD along the lines of "they used to tell us its good for the soul but then the government banned it because of flawed data against it"
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Capers
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Re: Organic Chemistry Homework Conundrum [Re: mellowparty]
#19009125 - 10/21/13 03:42 PM (10 years, 3 months ago) |
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I've got another one for you:

hint: Ethoxide ion is a base that can remove an acidic proton in an α-position to a carbonyl group, producing a nucleophilic enolate ion. Locate the α-hydrogens in the given molecule. What enolate ions can be formed in this reaction mixture?
hint 2: In the given structure there are two α-carbons that can lose a proton; therefore, two enolates are possible. To determine which enolate will yield the major product in this reaction, you need to consider the reaction mechanism. Compare the molecular formulas of the reactant and product. What does it tell you about the reaction? Which electrophilic site does the enolate attack?
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