Give the products that will be obtained from the following reactions if a. the reaction is carri

Give the products that will be obtained from the following...

Key Concepts

SN2 Reaction Mechanism

The SN2 mechanism involves a single concerted step in which the nucleophile attacks the electrophilic carbon from the opposite side of the leaving group. This backside attack leads to inversion of stereochemistry at the carbon center. SN2 reactions are favored by strong nucleophiles, less sterically hindered substrates, and polar aprotic solvents, which help stabilize the transition state and lower activation barriers.

SN1 Reaction Mechanism

The SN1 mechanism takes place in two steps: first, the leaving group departs, leading to the formation of a carbocation intermediate; then, the nucleophile attacks the planar carbocation. Because of the planar nature of the intermediate, the nucleophile can attack from either side, often resulting in racemization of the product. SN1 reactions are favored by substrates that stabilize carbocations (such as tertiary centers, resonance-stabilized systems) and occur in polar protic solvents which aid in carbocation formation.

Stereochemistry and Substrate Effects

The structure of the substrate plays a crucial role in determining the reaction pathway and stereochemical outcome. In SN2 reactions, the inversion of stereochemistry at the reactive center is a key feature, whereas in SN1 reactions the formation of a planar carbocation leads to a mixture of stereochemical outcomes. Additionally, the rigidity and ring structure of cyclic compounds can dramatically influence both the accessibility of the reaction center and the preferred mechanism, potentially affecting the products’ configuration and regiochemistry.

Solvent and Reaction Conditions

The reaction conditions, including the choice of solvent and the strength of the nucleophile or base, significantly influence whether a substitution reaction follows an SN1 or SN2 pathway. Polar aprotic solvents tend to favor SN2 reactions by not solvating anions too strongly, while polar protic solvents stabilize the carbocation intermediate, favoring SN1 reactions. Temperature and other reaction parameters may also contribute to the mechanism’s preference and the overall energy profile of the reaction.

Transcript

00:01 This question covers predicting the product of s in s in 2 reactions on the same substrate, and only varying the conditions.

00:10 So we're going to go ahead and start with this first example, which uses this cyclohexane compound here, that is trans between the bromal and the methyl substituing group.

00:26 And we are going to look and see what sort of product it would form for s in.

00:32 Conditions and s in s and two conditions.

00:35 So in s and one conditions typically we are going to be expecting to have all sorts of things that can stabilize the carbokadion intermediate, including the addition of heat, which would allow us to think that we might form a brief sketch here, a 1 4 hydride shift such that we get a tertiary carbokadion here.

01:05 On this location before i read the fourth position on the original molecule.

01:21 This would happen very rapidly so that we would not expect to see any of the secondary carbocadion intermediate.

01:28 And as a result, when this reacted with our methoxide nucleophile, we would expect to see roughly appear.

01:52 Sort of molecule that looks like this, where i'm keeping them in the, actually i'm going to go ahead and draw it and invert the stereochemistry like this, because that might be more likely to happen, although there would be a recemic mixture of the other way around.

02:19 And we're going to just draw this coming out of the page a little bit.

02:24 So plus the anantimer.

02:29 And our s &2 reaction, things are a little bit more straightforward, and we are just going to see a one -for -one switch of the bromine for the methoxide ion here, and we would expect to see converted stereochemistry, actually.

03:00 So we would expect to see the methyl oxide down here, with the age up here, looking like this.

03:09 So that's a two product with inverted stereochemistry, only forming one product, collect this in so you can see, turning out of the page...

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