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Topic: N Acidity/Basicity  (Read 3436 times)

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Offline Big-Daddy

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N Acidity/Basicity
« on: February 09, 2013, 12:44:16 PM »
Let there be six classes of N functional groups in organic compounds: tertiary amides (CONRR'), secondary amides (CONRH), primary amides (CONH2), tertiary amines (-NRR'), secondary amines (-NHR) and primary amines (-NH2). What is the order in which these are: a) likely to accept a new proton, and b) likely to lose one of their protons? And is the order of b) the opposite to the order of a)?

And before you ask, I have tried looking up pKa data but I'm just not sure what to look for. If you want to give me a list which would clarify the above, then please do; I will then look it up and bring any problems with interpretation back here. Also please remember that I'm looking for how the functional groups in general operate (within larger organic molecules), so please choose the compounds for which I should find the pKa accordingly.

Offline Dan

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Re: N Acidity/Basicity
« Reply #1 on: February 09, 2013, 01:00:22 PM »
There is a lot of material to cover here. There is a chapter devoted to the factors affecting acid/base strength of organic compounds in most organic chemistry textbooks - that is where you should start, there is too much to reproduce here.
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Offline Big-Daddy

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Re: N Acidity/Basicity
« Reply #2 on: February 09, 2013, 02:30:32 PM »
There is a lot of material to cover here. There is a chapter devoted to the factors affecting acid/base strength of organic compounds in most organic chemistry textbooks - that is where you should start, there is too much to reproduce here.

I'm asking just about nitrogenous functional groups, and that too only amides and amines, and I only want an overall general picture anyway. In the short term this is to answer exam questions specifically along the lines of "which atom is most likely to be protonated" or "which atom will be deprotonated in the compound", so for the time being I'm happy not to deal with more difficult real-world cases.

I don't have an organic chemistry textbook (nor do I need an undergraduate-level understanding of this, merely a high-school level one). Can you suggest where I could find the answers, online? I only want a "guesstimate" response, not an exact or completely reliable one.

Offline Dan

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Re: N Acidity/Basicity
« Reply #3 on: February 09, 2013, 02:40:02 PM »
I don't have an organic chemistry textbook (nor do I need an undergraduate-level understanding of this, merely a high-school level one).

I find this highly unlikely. I would strongly suggest you get at least one.

Quote
I'm asking just about nitrogenous functional groups, and that too only amides and amines, and I only want an overall general picture anyway.

You will get the general picture from the relevant chapter in most textbooks. Amides and amines are standard examples. The answers you are looking for are in the textbooks you claim you don't need - it is unlikely that anyone will be willing to reproduce it for you here.
My research: Google Scholar and Researchgate

Offline Big-Daddy

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Re: N Acidity/Basicity
« Reply #4 on: February 09, 2013, 03:08:07 PM »
I don't have an organic chemistry textbook (nor do I need an undergraduate-level understanding of this, merely a high-school level one).

I find this highly unlikely. I would strongly suggest you get at least one.

Quote
I'm asking just about nitrogenous functional groups, and that too only amides and amines, and I only want an overall general picture anyway.

You will get the general picture from the relevant chapter in most textbooks. Amides and amines are standard examples. The answers you are looking for are in the textbooks you claim you don't need - it is unlikely that anyone will be willing to reproduce it for you here.

The answer should be a simple list of 6 names! Why would you be unwilling to reproduce it?

As for my not needing an undergraduate-level understanding of this topic, the explanation would be that I am a high-school student revising for a high-school exam. I can make a more serious stab at undergraduate organic chemistry when I've got the high-school trivialities in place! At that point I will get the organic textbooks. Until then, though, I don't have long in which to have a basic framework to make good guesses for the questions high school examiners set! With that in mind, can you help me?

Offline Babcock_Hall

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Re: N Acidity/Basicity
« Reply #5 on: February 09, 2013, 05:47:53 PM »
Big-Daddy,

Within the series of primary, secondary, and tertiary amines, the order of base strength depends upon whether we are talking about water or talking about the gas phase.  In other words the solvent can overcome the intrinsic basicity.  See Table 3.12 in Mechanism and Theory in Organic Chemistry, 2nd edition, by Lowry and Richardson, 1981.

Offline Big-Daddy

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Re: N Acidity/Basicity
« Reply #6 on: February 10, 2013, 06:24:53 AM »
Big-Daddy,

Within the series of primary, secondary, and tertiary amines, the order of base strength depends upon whether we are talking about water or talking about the gas phase.  In other words the solvent can overcome the intrinsic basicity.  See Table 3.12 in Mechanism and Theory in Organic Chemistry, 2nd edition, by Lowry and Richardson, 1981.

What is the intrinsic order of basicity then? Is it really so hard for people just to type up two lists, if there are two lists (e.g. 1 for water, 1 for the gas phase) ... it's just 3 phrases per list  :P Please understand that I neither need exact ideas of strength nor have the ability to look up textbooks (though I can do internet searches if you tell me what to search for).

Offline Dan

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Re: N Acidity/Basicity
« Reply #7 on: February 10, 2013, 06:52:42 AM »
Is it really so hard for people just to type up two lists, if there are two lists (e.g. 1 for water, 1 for the gas phase) ... it's just 3 phrases per list  :P

Is it really so hard for you to open a book?

We do not dump answers here, we try to help you work it out - that is a forum rule. In order to work out the answer, you need to be aware of the basics of acid/base properties of organic compounds. We have told you where to find that information, and it is unlikely that anyone is willing to spend their time typing it all up just to save to a trip to the library. It is unreasonable to expect more effort from us than you are willing to put in.
My research: Google Scholar and Researchgate

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