New here... Discussing DAT Practice Problems

[Jay0689]

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Hi everybody,

Is this the place to discuss specific practice problems, from DAT Destroyer for example? Is there a single thread somewhere for this kind of thing?

For example, I'm wondering why an ammonium salt bonded to only 3 carbons and a hydrogen, HN(C2H5)3+ can be a quaternary amine (#12, 2011 Destroyer)? Is it the anion, which it would be ionically bonded to?

Thanks.

 

[HannibalLecter]

Hi everybody,

Is this the place to discuss specific practice problems, from DAT Destroyer for example? Is there a single thread somewhere for this kind of thing?

For example, I'm wondering why an ammonium salt bonded to only 3 carbons and a hydrogen, HN(C2H5)3+ can be a quaternary amine (#12, 2011 Destroyer)? Is it the anion, which it would be ionically bonded to?

Thanks.

No you got the wrong thread. I think you should find your answer in the for sale section. Haha. J/K you have come to the right place.

The reason this ammonium anion is a quaternary amine is because it has 4 groups attached to it instead of the regular tertiary amine like NH3 we are used to seeing. Since it has 4 groups attached to it hence it is a cation and would most likely be found in salt form with another anion. It is still considered an amine because it is attached to a hydrogen. And the anion would be something like chloride which carries a negative charge to balance the positive charge of this ammonium cation.

HN(CH3)3 + ----- Cl-

Thats what a compound you are talking about would look like

 

[smiley00]

Regarding nitrogen ...I was wondering would it be chiral with 3 diff groups? I know chirality is only for atoms w/ 4 diff groups attached to it...but I was doing a problem and it showed N as chiral b/c it had 3 groups diff attached to it. and i think the explanation said something like N wants to only have 3 groups attached to it. i was kinda confused? ...any thoughts?

 

[LetsGo2DSchool]

I thought H doesn't count as a group and thus it would be a tertiary amine since it's attached to 3 carbon groups.

Am I wrong?

 

[Jay0689]

Thanks for the help. I understand your point about the anion making it quaternary, so that takes care of my question. However I don't think NH3 is a tertiary amine. The H's don't count. For example, according to Destroyer, R-NH2 is a primary amine.

 

[HannibalLecter]

Ohhh yeah I used the NH3 as just an example to explain the bigger concept. NH3 is just ammonia no primary amine or what not.

 

[Jay0689]

Ok thanks. So if the counter ion for an ammonium salt counts and R3-NH+ is quaternary then what would R4-N+ be called? Is this a 5 degree ammonium salt since another C has been added to the N?

 

[Jay0689]

...And does this charge ruler apply to other atoms as well for deciding if it is primary, secondary, etc? Does a negative charge apply also?

 

[HannibalLecter]

Ok thanks. So if the counter ion for an ammonium salt counts and R3-NH+ is quaternary then what would R4-N+ be called? Is this a 5 degree ammonium salt since another C has been added to the N?

...And does this charge ruler apply to other atoms as well for deciding if it is primary, secondary, etc? Does a negative charge apply also?

Actually both of them would be considered quartenary ammonium salts:

Source: http://en.wikibooks.org/wiki/Organic_Chemistry/Amines

Its hard to differentiate between those two so when writing it out, I would include: (N,N,N)-Trimethylamine to signify how many groups there actually are.

Yes if it has more bonds than it usually does it would have a positive charge. I don't know if that answers your question but could you restate your second question again?

 

[Jay0689]

Thanks for your help Hannibal. I am wondering now if a charge will count as a carbon atom for this convention. For example, would NH2- be considered primary? And would the second carbon in the anion be considered secondary due to having a charge CH3CH2- ?

 

[HannibalLecter]

Thanks for your help Hannibal. I am wondering now if a charge will count as a carbon atom for this convention. For example, would NH2- be considered primary? And would the second carbon in the anion be considered secondary due to having a charge CH3CH2- ?

You will never be asked that but the charge does not count as a carbon. The NH2(-) would be considered an ??amonide?? but its definitely not a primary amine. The second carbon in CH3CH2(-) would be considered a primary carbon since it is only attached to a carbon. The classification of when it can be labeled as primary, secondary, tertiary is only when it is actually bound to a carbon not when it could be.