CH 220C Nucleophilic Substitution

2-chloro-2-methylbutane MSDS

severe FH NC NM

HCl MSDS

NFH NC PM

Sodium chloride MSDS

NFH NC NM

Sodium sulfate MSDS

NFH KC KM

Sodium bicarbonate MSDS

NFH NC PM

2-methyl-2-butanol MSDS

severe FH NC NM

Why is this reaction performed at room temperature and not at elevated temperature?

The product has a low boiling point and would evaporate, thus lowering the yield.

What type of reaction does the silver nitrate test undergo?

SN1, fastest with tertiary carbon

What type of reaction does the sodium iodide test undergo?

SN2, fastest with primary carbon

What is the fingerprint range on the IR spectrum?

400-1250

What is the functional group range on the IR spectrum?

1250-4000

Where is the C-H stretch in the IR spectrum?

3000-3100

Where is the C=O stretch in the IR spectrum?

1650-1750

Where is the O-H stretch in the IR spectrum?

3200-3600

How do you eliminate the OH peak if it shows up?

Dry solution with sodium sulfate

What indicates the IR has good data?

No OH peak

What kind of reaction is this experiment?

SN1

What determines the efficiency of a leaving group?

Conjugate acid strength

Why are there three washes?

to get rid of residual HCl and H2O

Why is anhydrous sodium sulfate added?

To remove as much water as possible

Procedure if HCl is ingested

Give water or milk

Purpose of alcoholic silver nitrate test

Confirms that OH was substituted by Cl

Purpose of sodium iodide in acetone test

Confirms that Cl is in the right place

White precipitate

AgCl

Pale yellow precipitate

AgBr

Dark yellow precipitate

AgI

What do extra peaks indicate in the IR?

impurities

What do missing peaks indicate in the IR?

incorrect analysis by the IR

Rules of the IR:

1. Clean area around instrument

2. Clean plate and aperture

3. No gloves

4. Click button once

5. Look at IR

Definition of a wash

liquid-liquid extraction where impurities are extracted from original solvent moving into the extraction solvent

What concentration of HCl is being used?

9-37%

Why is boiling point not used for analysis?

Harder to do and more prone to error

Properties of nucleophiles

1. At least one pair of non-bonding electrons

2. Neutral/negatively charged

A nucleophilic substitution where the nucleophile is a solvent

solvolysis

Why is the first step of an SN1 reaction the rate-determining step?

Unstable carbocation generation is endothermic

First-order rate constant

Rate = k1[R-L]

Second-order rate constant

Rate = k2[R-L][Nu]

Substitution is favored over elimination with ___ nucleophiles

weakly basic and highly polarizable

Elimination is favored over substitution with ___ nucleophiles

strongly basic and slightly polarizable

Bulky nucleophiles favor elimination because

the hydrogen atom is more accessible than the carbon atom with the leaving group

How is the E1 side product accounted for?

Markovnikov addition of HCl to the butenes

Alkyl bromides and iodides react ___ than alkyl chlorides

more rapidly

Aryl, vinyl, and alkynyl halides are ___ towards test reagent

unreactive

Allylic and benzylic halides are ___ due to ___

extremely reactive, resonance stabilization of carbocations

What is insoluble in acetone?

sodium chloride and sodium bromide

What is soluble in acetone?

sodium iodide

Bromide reaction rank

primary, secondary and tertiary at 50C

Chloride reaction rate

primary and secondary at 50C, tertiary fail to react

How much AgNO3?

2 mL 0.2 M

How much sodium iodide?

1 mL

What are the three washes?

sodium bicarbonate, sodium chloride, distilled water

What to do if negative absorbances are obtained?

take a background with sample on the plate, clean plate and take new background