Post-Lab: Substitution

Nucleophilic Aliphatic Substitution

Substitution of one group for another at a saturated, sp3-hybridized carbon; done to interconvert different functional groups.

SN1

- Slow reaction for heterolytic cleavage of LG (reversible; rate-determining step)

- Creation of a carbocation

- Fast reaction in which Nu attacks the carbocation

- Unfavorable for primary carbons

SN2

Nu directly attacks the molecule, and the formation of the C-Nu bond occurs simultaneously; no tertiary carbons.

Infrared Spectroscopy (IR)

Technique for identifying the presence of functional groups; allows you to form the molecule; no two compounds; no two compounds have the same R spectra

Halide Test

Test conducted to determine if we had completed our experiment correctly; Cl bonded on tertiary carbon

Nucleophilic Substitution Requirements

- Leaving group

- Nucleophile

- Why we chose HCl? Protonation of alcohol with HCl creates a good leaving group and Cl- can act as a Nu.

Difference between SN1 and SN2

SN1 occurs in two separate steps, while SN2 occurs simultaneously. SN2 does not occur in tertiary carbons.

Wash

Removing unwanted products

Extraction

Separating substances based on different solubilities; pulling a desired product.

Reaction and mechanisms of our reaction

- Protonation of the hydroxyl on the tertiary carbon via HCl to form LG

- H2O LG leaves the molecule and forms carbocation

- Cl- (Nu) attacks carbocation to form alkyl halide

IR Analysis

- C-H, Aromatics (weaker than alkanes), C=O (what type is it, 1650-1750, always strong absorbance), C-OH (can be strong or weak intensity or frequency)

- Peak Intensity: How much IR light is absorbed at a specific wavelength

- Peak Frequency: Speed of vibration or wavelength that a bond in a molecule absorbs

Percent Yield Analysis

1. Calculate theoretical: g of A / MW of A = mol of A * (mole ratio of B:A) = mol of B * MW of B = g of B

2. Calculate percent yield: Actual g of B / Theoretical g of B * 100

Halide Test Analysis

- Silver nitrate helps determine if a reaction undergoes SN1 if a precipitate forms.

- Sodium iodide helps determine if a reaction undergoes SN2 if a precipitate forms.