19. Aldehydes and Ketones:Nucleophilic Addition
Acetal
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General Mechanism
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in this page, we're gonna discuss another product that forms when carbon deal direct with alcohols, and that's called Assets House. So, guys, in general, I'm just gonna say a few fax and then we're gonna go straight into the mechanism. The first fact I want you to know is that a settles, once formed, are actually stable in base. Okay, so if you wanna keep it not settle for a long time, keep it in a neutral to basic solution. However, there easily hydrolyzed back to carbon eels using acid. And that makes sense, guys, because remember that this is a reversible reaction. It's acid catalyzed. So it makes sense that if you use acid, you're gonna go back to the carbon eel and it's gonna be an equilibrium. Okay, Now, if you want to specifically make an a settle that not only has r r O R O r, but it's actually cyclic, meaning it forms a ring. Then you're gonna have to use a dial, Okay, because the dialogue is gonna have carbons in the middle that are gonna link together. And so, for example, the dial that I would need here would be, ah 12 eh? Thin dial. Okay, Because as you can see, I've got my Oh, one, 234 I've got my 02 carbons in and Oh, and that's what I have here. 1234 So I would need a dialogue to make my cyclic at the top. Ok, now, let's just go straight into the mechanism for a settles on. What we'll find is that it? Actually, the only way to get to a NASA towel is to use the acid catalyzed mechanism. The base catalyzed mechanism is fine if you want to get to a Hemi hospital, but it's not gonna take you all the way to a full ass. It'll get to a full acquittal. You're gonna need to use the acid catalyzed mechanism. Okay, So that being said, let's actually start back from the beginning and just make it handy. Has to tell. And then I'm gonna show you guys how heavy is tell, Can you made into a nice hotel? So at this point, guys, you guys should be pros. We know that the first step is gonna be pro nation. Okay, just I'm just reiterating. Here is the same exact mechanism that we did for heavy as it sells. So now I've got my resident structure. I know that this positive on the O can resonate to the bottom so I could have a positive at the bottom as well. That shows how my carbon is being made. Hyper Electra, Filic and the alcohol could do a nuclear for, like, addition. Okay, so I do my nuclear feel like addition, I'm just gonna put here in nuclear feel like addition, okay? And then I'm sorry. And that this was Protein Nation. And then my last step was to do a deep throat nation with my conjugate base. Now, in this case, my conjugate base was alcohol. But whatever your conjugate base is, just depends on which acid you used. Not a big deal. So then I would do this. This is my de protein nation step. And we know that what we would get if drawing exactly the way we had it before was Ohh! Oh, are h h or how I like to draw it. Ohh! Oh, are each each okay? Plus my cadillac acid. So we're done with the heaviest tell part. How do we turn this into a a settle on, guys. It's almost the same exact mechanism is just gonna happen again. So now that we have our heaviest towel, we have to figure out, we know that we're gonna protein it against We're basically gonna go through a pro nation deep throat nation. Step again. But what do we protein eight. Do we protein ate the O H group or the O. R Group? How do I know which one? Well, to be honest, it could be either one The O H. Could protein eight or the O. R could protein eight. But the direction of your reaction depends on which one you protein, eight. If you wanna go towards the a settle, then that means you're trying to get rid of water, right? So then you should protein ate the O. H. If we're trying to go back to the original carbon Neil, then you're trying to get rid of the O. R. So you can reform the Carbonell. So in this case, I'm trying to go forward, so I'm gonna react with my o. H. Does that make sense, guys, literally. I'm choosing to use the O. H. Because I'm trying to draw the forward reaction But if you were drawing the backward reaction here, then we would use the O. R. This is going to give me a compound. It looks like this. So I'm gonna have oh h two positive h h o r. Okay, now, before in my other structure for him Until I had a resonant structure. In this case, I don't need one because the water is a great leaving group is just gonna take off by itself. Making a full car. Will cat iron. Okay, so we could against it. This was pro nation. I'm sorry. Yeah, pro nation. Okay. And then this would be, you know, forming formation of leaving group. Right? And then I would get I'm trying to use red here. Sorry. Then I would get nuclear feel like attack Nuclear Filic edition. Okay, so then I would get my nuclear feel like attack of the O to the sea. And that's going to give me my my tetra hydro carbon in the middle. At which point what's gonna be the last step? Deep Throat Nation. Guys, you got this case than 80 protein eight and I get my final compound that looks like oh, are o R h h, or the way that I like to draw it. Oh, are Pope are Ahh And you get your catalytic acid. Okay, guys, so really the Onley. It's a lot of steps, but it makes it easier The fact that you're doing the same thing twice, right? Also, the only really tricky part is that middle step with the heaviest. It'll figuring out which one to protein eat once you figure out which one to protein eight. Moving forward isn't hard at all. Okay, so guys, I hope that made sense. Now you guys know how to do a full acquittal mechanism? Just, you know, this is one of the most highly tested mechanisms in all of organic chemistry. So it's definitely when you want to commit to memory. It's definitely one that you could be asked to draw to some capacity or know about to some capacity on your exam. Alright, so that's it for this topic. Let's move onto the next one
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Problem
ProblemProvide the chemical steps necessary for the following synthesis.
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Problem
ProblemProvide the chemical steps necessary for the following synthesis.
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Problem
ProblemDetermine the starting materials based on the acetal group present.
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Additional resources for Acetal
PRACTICE PROBLEMS AND ACTIVITIES (19)
- What are the products of the following reactions? h.
- What are the products of the following reactions? f.
- What are the products of the following reactions? e.
- Which of the following are a. hemiacetals? b. acetals? c. hydrates? 2. (OCH2CH3)2CH3CH
- Which ketone forms the most hydrate in an aqueous solution? A. B.
- Propose a mechanism for each of the following reactions: b.
- Explain why acetals do not react with nucleophiles.
- Draw the products of the following reactions: a.
- Predict the products formed when cyclohexanecarbaldehyde reacts with the following reagents. (e) propane-1,3-...
- (b) The nucleosides that make up DNA have heterocyclic rings linked to deoxyribose by an aminoacetal function...
- For each compound, 1. name the functional group. 2. show what compound(s) result from complete hydrolysis. (c)...
- For each compound, 1. name the functional group. 2. show what compound(s) result from complete hydrolysis. (a...
- (d) Propose a mechanism for the acid-catalyzed hydrolysis of the acetal given in Problem 18-26(f).
- (b) Propose a mechanism for the acid-catalyzed hydrolysis of cyclohexanone ethylene acetal.
- Show what alcohols and carbonyl compounds give the following derivatives. (a) (b) (c)
- Draw structures of the following derivatives. (d) the ethylene acetal of hexan-3-one
- (a) Propose a mechanism for the acid-catalyzed reaction of cyclohexanone with ethylene glycol to give cycloh...
- Propose a mechanism for the acid-catalyzed hydrolysis of cyclohexanone dimethyl acetal.
- Propose a mechanism for the acid-catalyzed reaction of benzaldehyde with methanol to give benzaldehyde dimet...