Substitution Reactions Flashcards
What are the factors in determining SN1 vs SN2?
Firstly, the structure of the alkyl halide is the most impartant. Primary alkyl halides will ALWAYS undergo SN2 reactions, and tertiary alkyl halides will ALWAYS undergo SN1 reactions. Secondary alkyl halides are favored towards SN2 when the nucleophile is strong and when the solvent is polar aprotic, and are favored towards SN1 when the solvent is polar protic and the nucleophile is weak. Additionally, the stability of the carbocation contributes to a better or worse SN1 reaction.
How is stereochemistry affected by SN1 and SN2?
When there is a stereocenter, SN2 results in inversion of stereochemistry and SN1 results in racemization of stereochemistry.
What makes a strong nucleophile?
A higher negative charge makes a better nucleophile, and the better nucleophiles correlate with basicity (up and to the left) in polar aprotic, and to the left and down in a polar protic solution.
What contributes to the stability of carbocations?
How many R groups there are (electron donating via hyperconjugation), and how many electron-withdrawing groups there are, as well as if there is any resonance. Essentially anything to get more negative charge on the carbocation.
How many steps are SN1 vs SN2?
SN2 is one-step, whereas SN1 is multi-step (2 or more, often more).
