Assign configuration to the following substance, and draw the structure of the product that woul

Assign configuration to the following substance, and draw...

Key Concepts

Absolute Configuration Assignment

This involves determining the three?dimensional arrangement of the groups around a chiral center. The process consists of assigning an R or S designation to the chiral carbon, indicating the spatial order of atoms or groups relative to the molecule's configuration.

Cahn-Ingold-Prelog (CIP) Priority Rules

These rules provide a systematic method for ranking substituents attached to a chiral center based on atomic number and connectivity. By using the CIP rules, one assigns priorities that are critical for determining the absolute configuration (R or S) of a stereocenter.

Nucleophilic Substitution Reaction (S?2 Mechanism)

An S?2 reaction is a bimolecular process where a nucleophile attacks the electrophilic carbon from the opposite side of the leaving group. This single-step mechanism is characterized by its stereospecific nature, frequently leading to inversion of configuration.

Stereochemical Outcome (Walden Inversion)

In an S?2 reaction, the backside attack by the nucleophile results in an inversion of the configuration at the reactive center. This known phenomenon, Walden inversion, is essential for predicting the stereochemistry of the substitution product.

Transcript

00:01 All right, so here we have a bond line structure, which was drawn from a given bond stick model.

00:11 You should have a lot of practice with this already, but if you don't, just remember that bonds that are coming towards you are denoted with wedges, and bonds that are going away from you are denoted with lines.

00:25 So in this case, our bromo group is coming towards us, and our hydrogen group is going away from us.

00:30 So in this question, we are asked to first assign a configuration for the substance.

00:36 The first step when assigning configuration, if you recall, is that we have to assign priority groups to our chirocarbon.

00:43 In this case, our chirocarbon is the one with four different groups, which is circled in red here.

00:49 And so when assigning priority, we want to make sure that we give priority to the atom with the highest mass as our number one priority.

00:58 In this case, we have our bromine here with the highest mass.

01:01 So we would assign that with priority one.

01:04 And then we would assign this particular carbon, party two, because it actually has more carbons connected to it rather than this method group, which we would assign priority three.

01:14 And then our hydrogen, which is the lowest priority, we would assign priority four.

01:19 So since here, we see that we have a, looks like a counterclockwise.

01:26 When we go from one to two to three to four, it looks like we're going counterclockwise.

01:30 So we would denote this as a s configuration.

01:35 If we were going clockwise, we would denote that as an r configuration.

01:37 Since we are going counterclockwise here, it is s.

01:41 And the second part of the question, we are asked to predict if we are given the same structure.

01:50 So maybe draw the structure here.

01:57 So given the same structure, what would happen if we had a nucleophilic substitution reaction with the following nucleophile? say we had a hydrosulfide.

02:12 But we have to remember that there are two types of nucleophilic substitution reactions.

02:16 We can either have an s -n -1 or we can have an sn2.

02:22 So the question is, do we have an s -n -1 reaction or an s -n -2 reaction? well, remember that there are four characteristics to each substitution reaction that we have to analyze.

02:32 The very first characteristic is the substrate.

02:41 So in this case, we have our alkali halide, which is bromine, in the secondary position.

02:48 So typically with sn1 reactions, it favors tertiary as well as secondary alkyohylides, whereas sn2 favors primary and also secondary.

03:02 But since we have secondary, we're still unsure whether we have an sn1 or sn2...

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