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Topic: Alkyne rxns...?  (Read 5153 times)

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Offline Sonoris

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Alkyne rxns...?
« on: November 22, 2013, 01:02:42 AM »
Awful online homework, what else is new.


But afaik, these two don't even react? Solved

The textbook has nothing on alkynes + salts, just halides and stuff, so...?


It also says nothing about alkynes + these two, unless you also have some halogen stuff laying around to react with first...


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Edit2: What am I doing wrong here? It's neither of these apparently...?

« Last Edit: November 22, 2013, 03:23:13 AM by Sonoris »

Offline discodermolide

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Re: Alkyne rxns...?
« Reply #1 on: November 22, 2013, 01:25:44 AM »
So what is your question(s)? And have you any thoughts on the answers to your question(s)?
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Offline Sonoris

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Re: Alkyne rxns...?
« Reply #2 on: November 22, 2013, 01:30:05 AM »
So what is your question(s)? And have you any thoughts on the answers to your question(s)?

I have absolutely no idea how to go about these. The entire rest of the chapter questions I can do, but I can't find anything resembling these in the book. What is the mechanism going on here, and what would be the correct answer?

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Re: Alkyne rxns...?
« Reply #3 on: November 22, 2013, 01:34:03 AM »
Start with question A. It says acid/base reaction, so identify an acid and a base in that scheme.
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Offline Sonoris

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Re: Alkyne rxns...?
« Reply #4 on: November 22, 2013, 01:51:08 AM »
Start with question A. It says acid/base reaction, so identify an acid and a base in that scheme.
Acetylene is acidic, and NaOH is a base. Alright, so... an H can get pulled off the acetylene and there's gonna be ions and crap around and... ok, I got the right answer for it now. (quote from my textbook: "Because water is a stronger acid than acetylene, the hydroxide ion is not a strong enough base to convert a terminal alkyne to an alkyne anion" so uh, yeah...)

#2 still confuses me, but for #3 - is it just throwing a fit because I put NaNH2 and not Na+ and NH2- in the second box?

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Re: Alkyne rxns...?
« Reply #5 on: November 22, 2013, 02:54:11 AM »
Acetylene is acidic, and NaOH is a base. Alright, so... an H can get pulled off the acetylene and there's gonna be ions and crap around and... ok, I got the right answer for it now. (quote from my textbook: "Because water is a stronger acid than acetylene, the hydroxide ion is not a strong enough base to convert a terminal alkyne to an alkyne anion" so uh, yeah...)

There is no NaOH in the question.
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Offline Archer

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Re: Alkyne rxns...?
« Reply #6 on: November 22, 2013, 02:57:52 AM »

but for #3 - is it just throwing a fit because I put NaNH2 and not Na+ and NH2- in the second box?


Is that NH2- or NH2-?
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Offline Sonoris

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Re: Alkyne rxns...?
« Reply #7 on: November 22, 2013, 03:04:38 AM »
Acetylene is acidic, and NaOH is a base. Alright, so... an H can get pulled off the acetylene and there's gonna be ions and crap around and... ok, I got the right answer for it now. (quote from my textbook: "Because water is a stronger acid than acetylene, the hydroxide ion is not a strong enough base to convert a terminal alkyne to an alkyne anion" so uh, yeah...)

There is no NaOH in the question.
The now-solved, strikethrough question had NaOH

Offline Sonoris

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Re: Alkyne rxns...?
« Reply #8 on: November 22, 2013, 03:05:25 AM »

but for #3 - is it just throwing a fit because I put NaNH2 and not Na+ and NH2- in the second box?


Is that NH2- or NH2-?
NH2-

Offline discodermolide

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Re: Alkyne rxns...?
« Reply #9 on: November 22, 2013, 03:22:10 AM »
same thing which is the acid and which the base?


did you delete the previous one? If so please don't.
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Offline Sonoris

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Re: Alkyne rxns...?
« Reply #10 on: November 22, 2013, 03:39:32 AM »
same thing which is the acid and which the base?


did you delete the previous one? If so please don't.
No, I turned the statement into a link to the picture and put solved next to it - still there, just not obnoxiously huge.

Acetylene is still the acid, and the... lithium thing is the base I guess. If it's like the last one, ...oh, REALLY. That double bond in my answer should be a triple. Would that make it correct?

For the next one, with the alcohol + NaNH2 + NH3 - it won't accept any type of answer I think it might be (see Edit2, same issue)

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Re: Alkyne rxns...?
« Reply #11 on: November 22, 2013, 03:42:10 AM »
OK, the ethyl lithium is the base the acetylene the acid, so what could the products be?

Same for the alcohol, what are the products?
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Offline discodermolide

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Re: Alkyne rxns...?
« Reply #12 on: November 22, 2013, 04:01:54 AM »
Think about the very first question, what did you do to get the answer?
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Offline Sonoris

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Re: Alkyne rxns...?
« Reply #13 on: November 22, 2013, 04:15:31 AM »
OK, the ethyl lithium is the base the acetylene the acid, so what could the products be?

Same for the alcohol, what are the products?
For the lithium one - I want to say it'd be this, but in drawing it out I get this, but I guess the Li+ would go hang out with the C-

For the -OH one, the OH compound is the base and the other is the acid. I still stand by the organic part of my answer, but... I guess there would just be Na+ around instead of NaNH2
edit: this answer for my -OH problem doesn't help for the edit to the main post I made, since neither of those are right and it just wanted the organics

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Re: Alkyne rxns...?
« Reply #14 on: November 22, 2013, 04:20:02 AM »
The acetylene one is now ok, you get
[C-]#C[H].[Li+]
and ethane.

Now do the same for the alcohol, replace the O-H by O-Na+ and the NH2- by NH3.
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