Chapter 8 - Nucleophilic Substitution Chapter 8...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Nucleophilic Substitution Chapter 8 Nucleophilic Substitution • R = alkyl group • X = leaving group • Y = nucleophile • Convenient means of functional group transformations – R X transformed to R Y Nucleophilic Substitution • Nucleophilic substitution with alkyl halides is convenient means to prepare a variety of compounds • Extremely useful reaction because alkyl halide are readily accessible: R OH R C=CR R-X Alkyl halide R-OH Alcohol CHR 3 Alkane R 2 C=CR 2 Alkenes Radical halogenation (e.g., X 2 + h ν ) Addition (e.g., HX) Nucleophilic Subst. (e.g., HX) R-Nu NaI is soluble in acetone; NaCl and NaBr are not soluble in acetone. Nucleophilic Substitution Examples • When the substitution product bears a positive charge and also contains a proton bonded to O or N, the initially formed substitution product readily loses a proton to form a neutral product. Nucleophilic Substitution Examples Leaving Group • For example, H 2 O is a better leaving group than HO¯ because H 2 O is a weaker base. Leaving Group Leaving Group Leaving Group A single organic product was obtained when 1-bromo-3-chloropropane was allowed to react with one molar equivalent of sodium cyanide in aqueous ethanol. What was this product? Problem 8.2 S N 2 Example Stereochemistry of S N 2 Reactions Stereochemistry of S N 2 Reactions Steric Effects in S N 2 Reactions 221,000 1,350 1 Too small to measure Relative rates of S N 2 with Li I • Nucleophiles and bases are structurally similar • Both have a lone pair or a π bond. • They differ in what they attack. Nucleophiles vs. Bases • Though nucleophilicity and basicity are interrelated, they are fundamentally different. Basicity is a measure of how readily an atom abstracts a proton. Characterized by an equilibrium constant ( K a ) in an acid-base reaction, making it a thermodynamic property . Nucleophiles vs. Bases Nucleophilicity is a measure of how fast an atom donates its electron pair to other atoms (usually carbon). Characterized by a rate constant, k , making it a kinetic property . It is generally true that a strong base is a strong nucleophile • Nucleophilicity parallels basicity in three instances: 1. For two nucleophiles with the same nucleophilic atom and similar sterics, the stronger base is the stronger nucleophile ....
View Full Document

This note was uploaded on 12/22/2011 for the course CHEM 3371 taught by Professor Anderson,k during the Fall '08 term at Southern Methodist.

Page1 / 29

Chapter 8 - Nucleophilic Substitution Chapter 8...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online