Draw the mechanism for formation of the two addition products....

Question

Draw the mechanism for formation of the two addition products.

Accepted Answer

Hey, everyone and welcome back, suggest a plausible mechanism for the base catalyzed ring opening of benzene oxide in your mechanism. Use new minus as a generic nu file. First of all, let's draw benzene oxide. So that would be our six member grain, right? Because we have benzene, we are going to add our double bonds. And now we are going to add our three membered ring between two carbon atoms and oxygen. As the problem suggests, we have a generic nuclear file new minus. And specifically because we have a base catalyzed ring opening, we have to recall that we will observe an S N two type of a reaction in which a less substituted carbon will be attacked, right? That's really important in a base catalyzed ring opening, the less substituted carbon is attacked as per STAIC considerations that favor an essence of reaction in acidic conditions, the more substituted carbon gets attacked. But if you carefully look at the reaction and in particular at the starting material, the two electrophysics centers are equally substituted. So we have two possibilities. And let's look at both of them, let's look at one of them and let's use a green color code. So the nuclear file attacks and during the attack stop, we are opening our ring, right? And for complete clarity, for complete clarity, I'm sorry, it's really important to think about our bonds. Let's think about the spatial arrangement of our substituent and we can consider our oxygen pointing up on two wedges, right? Or two dashes. It doesn't really matter because the structure is symmetrical. So it's a measle compound, right? You can essentially rotate and you will obtain two dashes so that oxygen will be pointing down. So let's use that representation of our benzene oxide. Now, the nuclear file attacks followed by the loss of the leaving group just as defined by an essence of reaction. And we will observe an inversion of configuration right at the center. So we can now redraw our six member ring, our double bonds and we will have an inversion of configuration because that's an essence two reaction and we have a backside attack. So the nuclear file will now be pointing down instead of having a wedge which represents a bond pointing up at the adjacent position, the oxide and I will be still pointing up because no reaction took place there. Now, whenever we have a base catalyzed ring opening, we have a solution. So we will also have a conjugate asset of our nu file which will correspond to H or hydrogen bonded to our nuclear file, which will essentially act as a proton donor right. So we are going to restore the negatively charged nuclear file. That's why it's called the base catalyzed ring opening. We are restoring the nuclear file used and therefore, we are ready to draw the first product specifically, nothing much changes except from the fact that we are now adding a proton to our oxygen to form the final alcohol. Well done. We are also going to add our negatively charged nuclear file as a byproduct. And now for the second pathway, let's consider it. And we understand that we can also attack the other position. Let's use a blue color code. So we're going to attack the electrolytic position followed by the loss of the leaving group. And now we will essentially get a pair or basically an in an humor to the previous structure, right? If you carefully consider it, you are going to get the six number ring. Now the nu fi is going to be bonded to our carbon, we're going to use a dash, right? Because we have an inversion of configuration and now oxygen will be pointing up on a watch. OK. And similarly to what we observed before, we are now going to use our conjugate asset of the base, which will proton oxygen and we will get the alcohol group. So we can easily draw our found product by adding hydrogen to oxygen and obtaining our final alcohol. In addition to that, we will state that the byproduct is our negatively charged nu formed in the previous step. And we simply got a pair of an anti right. You may notice that if you slightly rotate the second structure, you will obtain non superimposable mirror images of each other. That's it. We are going to label our final products and we are going to briefly review the mechanism. We understand that the structure is a meso compound. So we have chosen two wedges, although you can choose two dashes for the starting material, the nu file corresponds to a base caty ring opening so that two positions can be attacked because they are both equally substituted, attacking the first position. We have a backside attack followed by the loss of the leaving group. And ALCO gets protend to form the final alcohol and we observe the same pattern. But from a different side, we have another backside attack and we are obtaining our final product. Notice how each product has anti arrangement between our alcohol group and the nuclear file. Thank you for watching.

Draw the mechanism for formation of the two addition products.

Key Concepts

Nucleophilic Addition

Reaction Mechanism

Stereochemistry

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