OChem Destroyer # 83

[jwnichols21]

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Which of the following describes the role of propyne in the acid-base reaction shown?

CH3-C(triple bond)C-H + NH2

It shows the electron pair on the nitrogen attacking the H attached to the triple bonded-C.

A) Bronstead-Lowry Acid
B) Bronstead-Lowry Base
C) Lewis Acid
D & E) -------- (stupid choices)

SO the answer is A. But I really think that it also should be C because it is in fact a Lewis Acid, right? Propyne is RECEIVING electrons from the H when the H gets abstracted by the amine. Thus the amine is DONATING e- pair (lewis base) and the propyne is ACCEPTING an e- pair (lewis acid).

What am I missing here? Thanks.

 

[LuckyTangerines]

Which of the following describes the role of propyne in the acid-base reaction shown?

CH3-C(triple bond)C-H + NH2

It shows the electron pair on the nitrogen attacking the H attached to the triple bonded-C.

A) Bronstead-Lowry Acid
B) Bronstead-Lowry Base
C) Lewis Acid
D & E) -------- (stupid choices)

SO the answer is A. But I really think that it also should be C because it is in fact a Lewis Acid, right? Propyne is RECEIVING electrons from the H when the H gets abstracted by the amine. Thus the amine is DONATING e- pair (lewis base) and the propyne is ACCEPTING an e- pair (lewis acid).

What am I missing here? Thanks.

The Propyne is a Bronsted-Lowry Acid because, by definition, it is donating a proton to NH2. So this is the best answer to choose from out of the choices given.

A Lewis Acid is an electron pair acceptor. So it is an electrophile basically. An example would be BF3 since it can accept a pair of electrons to complete an octet.

Sometimes I get confused with these acid base definitions myself but just remember them. I always reviewed the examples Chad had in one of his GC videos. Good luck!

 

[jwnichols21]

The Propyne is a Bronsted-Lowry Acid because, by definition, it is donating a proton to NH2. So this is the best answer to choose from out of the choices given.

A Lewis Acid is an electron pair acceptor. So it is an electrophile basically. An example would be BF3 since it can accept a pair of electrons to complete an octet.

Sometimes I get confused with these acid base definitions myself but just remember them. I always reviewed the examples Chad had in one of his GC videos. Good luck!

In Chad's example (GChem 5.05) he has NH3 pulling an electron off of H-Cl and he says that HCl is the Lewis Acid. How is this any different than the problem above?

 

[needzmoar]

the propyne is a bronsted-lowry acid because, by definition, it is donating a proton to nh2. So this is the best answer to choose from out of the choices given.

A lewis acid is an electron pair acceptor. So it is an electrophile basically. An example would be bf3 since it can accept a pair of electrons to complete an octet.

Sometimes i get confused with these acid base definitions myself but just remember them. I always reviewed the examples chad had in one of his gc videos. Good luck!

+1

 

[LuckyTangerines]

In Chad's example (GChem 5.05) he has NH3 pulling an electron off of H-Cl and he says that HCl is the Lewis Acid. How is this any different than the problem above?

Chad says that if the acid/base fits the Bronsted definition, then it also fits the Lewis definition; however, an acid/base that fits the Lewis definition doesn't necessarily fit the Bronsted definition.

He explains in the example how the acid and base fit according to Bronsted's definition first. And because they fit that definition, they also fit the Lewis definition. So you're right HCL is a Lewis acid.

I can kind of see how the answer in destroyer can be Lewis answer as well. But when I initially see the reaction, I immediately see a transfer of protons and picked Bronsted acid. With multiple choice, you want to pick the best answer Bronsted acid is the better answer because by choosing that, you're also saying it is a Lewis acid acid. Hope this helps!

 

[jwnichols21]

Chad says that if the acid/base fits the Bronsted definition, then it also fits the Lewis definition; however, an acid/base that fits the Lewis definition doesn't necessarily fit the Bronsted definition.

He explains in the example how the acid and base fit according to Bronsted's definition first. And because they fit that definition, they also fit the Lewis definition. So you're right HCL is a Lewis acid.

I can kind of see how the answer in destroyer can be Lewis answer as well. But when I initially see the reaction, I immediately see a transfer of protons and picked Bronsted acid. With multiple choice, you want to pick the best answer Bronsted acid is the better answer because by choosing that, you're also saying it is a Lewis acid acid. Hope this helps!

Ah, thank you. That is tricky, but makes sense.