Propose a mechanism for each reaction, showing explicitly how ...

Question

Propose a mechanism for each reaction, showing explicitly how the observed mixtures of products are formed.

(e) 3-chlorobut-1-ene + AgNO₃, H₂O → but-2-en-1-ol + but-3-en-2-ol

Accepted Answer

All right. Hello everyone. So this question is asking us to suggest a mechanism for the reactions shown below. And here we have three Chloro 23 dimethyl butte one in and silver nitrate with water producing 23 dimethyl butte three E 20 and 23 dimeo butte two in 10. So first, let's illustrate the reaction provided here, our starting material is three chloro 23 dimethyl butte one E. So first, thats a four carbon parent chain with a double bond in between carbons, one and two, two methyl substituents one on carbon two and the other on carbon three and a chlorine attached to carbon three as well. So our starting material is reacting with silver nitrate, that's no three in the presence of water. And after this, we end up with two different products. The first is 23 dimethyl butte three in to all. So that's the same or carbon parent chain with a double bond in between carbons three and four of the parent chain. Two methyl substituents one on carbon number two and the other on carbon number three and a hydroxy substituent or an O group on carbon number two. Our second product is 23 dimethyl butte two in 10. So we have yet another or carbon parent chain this time with a double bond in between carbons two and three, the hydroxy substituent on carbon number one and one methyl substituent on carbons two and three. All right. So here, now that we have a sense on what has changed when comparing the starting materials to the products. Let's recall the role of silver nitrate. When silver nitrate is mixed with an oy Halide, the formation of a carbo cion is favored. The reason for this is because the halogen is going to create a bond with silver and create an insoluble silver hide. So if we consider our starting material, our halogen here, our chlorine is attached to a carbon that is sp three hybridized and adjacent to an alkene to a double bond. We call this an aic carbon and a lilic carbons make fantastic carbo CS because they are resonant stabilized. So because of this resonance stabilization, there are two different possibilities. Either the double wand stays at the end of the carb chain or it migrates to the center of the carbon chain. Because of that resonance de localization. This creates two possible locations for nucleic attack because that positive charge migrates our other reagent water is going to behave as a nucleo and attack either position resulting in the two different products. We notice here after the detonation of that water molecule after nucleic attack. So with this in mind, let's go ahead and showcase how that happens. And I'm going to start by copying and pasting this drawing of the starting material. So now we have the starting material on the bottom here. And for the first step of the reaction, I am going to go ahead and just showcase the silver C that we have in solution. So at this point because the silver cion is in solution, the bond between carbon and chlorine is going to break using those same electrons from the covalent bond, chlorine is going to establish a bond with the silver cion to create insoluble silver chloride. So as a result, we end up with the same carbon chain with the same substituents as well. But the difference now is that carbon three of the parent chain is going to have a positive charge. And because we now have an aic carbo cion, it is resonance stabilized. So I'm going to enclose our resonance forms in brackets. Currently, the pi bond is in between carbons one and two of the parent chain recall it resonance is always going to be a movement from a region of higher electron density towards a region of lower electron density. Because of this, the pi electrons of the keen are going to migrate towards the positive charge. What this does is ultimately move the pi bond in between carbons two and three instead. So now the positive charge is going to be on carbon one of the parent chain. So now these are all of our resonance forms. So I'm going to close my brackets here. And now the reason we end up with two distinct products is because there are two different locations for that nucleic attack water can attack the initial carbo cion or it can attack carbon one of the parent chain after the positive charge migrates there because of resonance. So here I'm going to scroll down so I can open up some space and I am actually going to make this drawing slightly smaller just so you could see it on the screen. All right. So here I'm going to go ahead and have water attack either carbo cion. But I'm going to show that reaction using a different colored arrow, let's say a red arrow. The reason for this is because I want to distinguish this reaction arrow from the arrows that we used to describe resonance or to showcase the residence de localization. So first water can go ahead and attack the cruel cion on carbon three of the parent chain or it can attack the carbo cion at position one. This means that water can be attached now to either carbons three or one. And at this point, I also want to point out here that the oxygen atoms from those water molecules that served as NUC files currently have three covalent bonds and only one pair of electrons because of this, both of them are actually going to have a positive formal charge, which is why the final step is actually derotation using another molecule of water. So for both drawings here, I'm going to have a molecule or an additional molecule of water serve as a base to create neutral hydroxy groups. So the other molecule of water takes the proton which thereby gives are positively charged oxygens and extra loan pair of electrons thereby making them neutral. So now this creates 23 dimeo butte three in 20 and 23 dimethyl butte two in one all and there you have it. So here is our complete mechanism. But before I go ahead and highlight it, I do want to make a quick correction to the products that I drew earlier on in this video because in my initial drawing of 23 dimethyl butte two in 10 I drew carbon number one as ach three when it should actually be ach two. So I just wanna fix that right here. But with that being said, if you watch this video all the way through, thank you so very much. And I hope you found this helpful.

Propose a mechanism for each reaction, showing explicitly how the observed mixtures of products are formed.
(e) 3-chlorobut-1-ene + AgNO₃, H₂O → but-2-en-1-ol + but-3-en-2-ol

Key Concepts

Electrophilic Addition Reactions

Regioselectivity

Carbocation Stability

Watch next