Draw a perspective structure or a Fischer projection for the products of the following S_N2 reactions.
(c)
(d)

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Step 1: Identify the reaction type. Both reactions are SN2 reactions, which involve a backside attack by the nucleophile and inversion of stereochemistry at the carbon center where substitution occurs.

Step 2: Analyze the first reaction. The substrate is a brominated compound in a Fischer projection. The nucleophile is iodide (I⁻), and the solvent is acetone, which is polar aprotic and favors SN2 reactions. The iodide will replace the bromine via backside attack, leading to inversion of stereochemistry at the carbon center.

Step 3: Draw the product for the first reaction. Replace the bromine atom with iodine, ensuring the stereochemistry is inverted. In a Fischer projection, inversion means swapping the positions of the groups attached to the carbon center where substitution occurs.

Step 4: Analyze the second reaction. The substrate is a brominated compound in a perspective structure. The nucleophile is the thiolate ion (SH⁻), which will replace the bromine via backside attack. Again, inversion of stereochemistry occurs at the carbon center.

Step 5: Draw the product for the second reaction. Replace the bromine atom with the SH group, ensuring the stereochemistry is inverted. In a perspective structure, inversion means flipping the wedge and dash positions of the substituents at the carbon center where substitution occurs.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

SN2 Mechanism

The SN2 mechanism is a type of nucleophilic substitution reaction where a nucleophile attacks an electrophile, resulting in the simultaneous displacement of a leaving group. This reaction occurs in a single concerted step, leading to the inversion of configuration at the carbon center. It is characterized by a second-order kinetics, meaning the rate depends on the concentration of both the nucleophile and the substrate.

Fischer Projection

A Fischer projection is a two-dimensional representation of a three-dimensional organic molecule, particularly useful for depicting stereochemistry. In this format, vertical lines represent bonds that project away from the viewer, while horizontal lines represent bonds that come towards the viewer. Fischer projections are commonly used to illustrate carbohydrates and amino acids, allowing for easy identification of stereoisomers.

Nucleophiles and Electrophiles

Nucleophiles are species that donate an electron pair to form a chemical bond, while electrophiles are electron-deficient species that accept an electron pair. In SN2 reactions, the nucleophile attacks the electrophile, leading to the substitution of the leaving group. Understanding the nature of these species is crucial for predicting the outcome of organic reactions and determining reaction mechanisms.

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