Predict the product of the following substitution reactions, m...

Question

Predict the product of the following substitution reactions, making sure to note whether a rearrangement should occur.

(b)

Accepted Answer

All right. Hi, everyone. So for this question, let's go ahead and draw the major product or products of the substitution reaction. Below note, make sure to consider possible rearrangements. Our starting material is one R two S one Chloro two methyl cyclops in methanol. Scrolling down here, we can see options A and B once more for options C and D. So lets go ahead and get started. Now because the question mentions that this is going to be a substitution reaction. We have to differentiate between whether this is going to be an SN one mechanism or an SN two mechanism. Factors that we would consider include the nucleo files, strength, the leaving group substitution and the solvent. Now, our organic starting material contained chlorine, which is going to function as our leaving group because chloride is a weak base. So here we can see that our chlorine atom is connecting to a secondary carbon on the cyclops ring. Recall that secondary leaving groups can favor either SN one or S and two mechanisms. So we're going to have to rely on other information, two, decide on one mechanism over the other. Now, in this case, our other reagent happens to be methanol. And this reaction is an example of a process known as Solvo isis. Now, Solvo assis is a substitution reaction in which the solvent is also the nuclei. And because methanol is neutral, it's considered to be a quote unquote weak nucleo, which if you recall favors SN one mechanisms since SN two mechanisms favor stronger, negatively charged N files. So our Nile is quote unquote weak and our solvent which is also the Nile that's methanol is polar product, which also favors SN one recall that a solvent is considered to be polar protic if it has a proton connecting to an electron element such as oxygen, nitrogen and fluorine. So now let's go ahead and talk about the Essen one mechanism. The essen one mechanism is characterized by the formation of a carbo cion intermediate. Whereas S and two reactions are concerted in which the Nile attacks and the leaving group leaves in the same step. So, in the case of our S and one mechanism here, the first step is going to involve the departure of the leaving group to form a carbo cion. So Chine is going to detach itself from carbon while also taking the electrons connecting chlorine to carbon that results in the car cat. So as a result, I should open up some space here. All right. So now chlorine has since left and that results in a positive charge on that secondary carbon. Now, because our SN one mechanism does feature the formation of a carbo cion recall that rearrangement should always be something to check for. Because if a carbel cion can move to a different position to achieve greater stability, it's going to do. So. In this case, our secondary carbo cion is next to a tertiary carbon and that tertiary carbon has a hydrogen atom. This means that the hydrogen atom can undergo a hydride shift to result in a Carbocaine on the tertiary position. So that's precisely what's going to happen, right. So hydride or hydrogen with a lone pair of electrons is going to move from that tertiary carbon onto the secondary position. This results in the formation of a reel cion on that tertiary position. So now that the carbo cion has rearranged, I can very quickly talk about the stereo chemistry of the SN one mechanism recall that carbo C ions are plainer, which means that they lie flat. So during the next step, which involves nucleic attack, the nucleo file can attack the carbo cion either in front or behind the Carbocaine itself. Normally, this would result in a mixture of stereo isomers after an sn one process. However, it's worth mentioning that the current carbo cion has an element of symmetry to it. This means that the products formed would actually be the same regardless of the direction of the nucleo files attack. So from this point onwards, I'm not going to showcase any stereo chemistry using wedges or dashes because in this case, it's not relevant, but just keep that in mind. So with that being said, we can go ahead and introduce methanol, right, the nucleic portion of methanol is the oxygen atom that contains alone pairs of electrons. So those lone pairs are going to attack the tertiary carbon with a positive charge. So at this point, we now have a bond between the oxygen of methanol and the tertiary carbon. But because this oxygen is in alcohol, there's still a proton attached at this point, meaning that after nucleic attack, oxygen actually has a positive charge. So because oxygen has a positive charge at this point, there is one more step that's necessary, this oxygen atom must be detonated to produce a neutral product. So because methanol is our solvent, in addition to our nucleo file, a second molecule of methanol is going to go ahead and detonate our oxygen here. That's going to take this proton. And that's going to restore a neutral charge on that oxygen. This gives us our final product in which there is now a meth boxy group attached to the tertiary carbon. And so this matches with option D in our multiple choice. So that's going to be our final answer and there you have it. So the main point here is that this reaction was an example of Solvo sis which is an SN one mechanism or s and one reaction in which the solvent is also the nuclei. After a crumble cat on rearrangement, we end up with a me foxy substituent attached to the same carbon as the methyl group. In our starting material. In this case, stereo chemistry is not relevant due to the element of symmetry present in the Carbocaine intermediate. So with that being said, if you watch this video all the way up to the end, thank you so very much and I hope you found this helpful.

Predict the product of the following substitution reactions, making sure to note whether a rearrangement should occur.
(b)

Key Concepts

Nucleophilic Substitution Reactions

Mechanism of SN1 and SN2 Reactions

Carbocation Stability and Rearrangement

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