Chemistry 234

Organic Chemistry Laboratory

Stan Smith [email protected] www.chem.uiuc.edu

User Name: netID Password: netID No - in netID Change your password! ChemNet

Requires Microsoft Internet Explorer 2 points/lesson Due May 2, 2001 Laboratory Notebook Reference Data Observations Properties: compounds solvents Laboratory Reports Safety Equipment Eye wash faucets Eye wash bottles Overhead showers Fire blanket Fire extinguishers Fire-emergency alarm box First-aid box Exits Room 467 Noyes Lab

Mark location of safety equipment on map of room. Contact your TA immediately Grades Laboratory Reports 230 2 50 minute Exams 2x100 = 200 On-line Quizzes 10*10 = 100 ChemNet 16*2 = 36

15% A 30% B 50% C 5% D + E Hour Exam Dates

Dates: Exam 1: Thursday, March 1, 2001 Exam 2: Wednesday, April 25, 2001

Time: 7:00 p.m. Breakage Replacement Card Change Section - Makeup Labs

Mike Eubanks 469 Noyes Lab Melting Points and Mixed Melting Points

Experiment 1: Identify a compound by its melting point and mixed melting points.

Acetamide 113 - 115 oC p-Aminobenzoic acid 188 - 189 oC Camphoric Acid 183 - 186 oC trans-Cinnamic Acid 133 - 134 oC Malonic Acid 135 - 137 oC p-Nitrophenol 113 - 115 oC Resorcinol 110 - 113 oC Succinic Acid 187 - 189 oC Urea 133 - 135 oC A sample is put in the bottom of a melting point tube. Put a small amount of the compound in the open end of the melting point tube.

Turn over and tape the closed end on the desk top until the compound falls to the bottom. Sample in the melting point tube. Use a Thiele tube filled with mineral oil to heat your sample. Attach the melting point tube to a thermometer. Heat about 5o per minute until within about 10o of the melting point

Near the melting point heat at 1 - 2o per minute Mel-Temp in the lab Temperature

Starts to melt Finished melting

m.p. = Start - Finish Why is salt put on snow covered roads? Ice melts at 0oC

What happens to the melting point if salt is added?

Ice melts! Impurities such as salt lowers the melting point of water.

Putting salt on icy roads causes the ice to melt because it lowers the melting point of water.

Impure compounds usually melt lower than pure compounds so the melting point may be used as a measure of the purity of a compound Acetic Acid, CH3COOH, is a colorless liquid that melts at 16.6oC.

Let’s look at the melting point of mixtures of water and acetic acid. Plot of melting point vs. mole fraction water for mixtures of water and acetic acid.

Eutectic point Cool a acetic acid - water solution with a mole fraction water of 0.9 Heat a acetic acid - water solution with a mole fraction water of 0.9 Heat a acetic acid - water solution with a mole fraction water of 0.2 Pure compounds usually melt over a narrow temperature range, often 1o or less.

Impure compounds melt lower than pure compounds and over a wider temperature range. Melting points are a measure of purity

m.p. = 115o - 119o m.p. = 118o - 120o m.p. = 121o - 122o Two of these bottles contain benzoic acid and one m-nitrophenylacetic acid.

m.p. = 120o - 122o m.p. = 120o - 122o m.p. = 120o - 122o

How do you tell what is in each bottle? Mixed Melting Points

Grind samples together to be sure they are mixed and then measure the melting point. Results

123 Mixed 1 and 2 m.p. = 120o - 122o

Mixed 1 and 3 m.p. = 114o - 117o

Mixed 2 and 3 m.p. = 115o - 118o 1. Measure the melting point of your unknown

2. Run mixed melting points to confirm identification Recrystallization

Impure benzoic acid

Benzoic acid after recrystallization O C-OH

Benzoic Acid m.p. = 121 - 122o Purification of Organic Compounds

Solids: Recrystallization

Liquids: Distillation

Solids and Liquids: Gas or liquid chromotography Types of impurities Soluble Insoluble Partly Soluble Solubility of benzoic acid in water Dissolve sample in hot solvent

Compound crystallizes upon cooling Impure benzoic acid in hot water Add water and heat until all soluble material dissolves

Insoluble material is removed by filtration The hot solution is filtered to remove insoluble impurities Use fluted filter paper to maximize surface area. To avoid crystallization in the funnel:

Use GLASS funnel. Put flask on hot plate. Boil off excess solvent Boiling Sticks Hot solution after filtration:

Cool Seed Scratch Crystals form in the warm solution

Next: Cool, filter, wash, dry, weigh, mp

.. Buchner funnel Heavy-walled tubing

Filter flask Vacuum Put filter paper in Buchner.. funnel Filter and wash with cold solvent Insoluble Soluble Purified impurities impurities benzoic acid Solubility Example

Compound Solubility g/100 mL 25o 100o

A 1.0 80 I1 1.5 50 I2 0.0 0.0 Solubility g/100 mL Compound 25o 100o A 1.0 80 I1 1.5 50 I2 0.0 0.0 A = 10 g I1 = 1.0 g I2 = 1.0 g Total = 12.0 g

100 mL water at 1000 A dissolves I1 dissolves I2 insoluble Solubility g/100 mL Compound 25o 100o A 1.0 80 I1 1.5 50 I2 0.0 0.0

A = 10 g I1 = 1.0 g I2 = 1.0 g Total = 12.0 g

100 mL water at 1000 Cool to 25o

A dissolves A 9.0 g crystallize

I1 dissolves I1 0 g crystallize I2 insoluble Yield = 100 * 9.0/12.0 = 75% Solubility g/100 mL Compound 25o 100o A 1.0 80 I1 1.5 50 I2 0.0 0.0

A = 10 g I1 = 1.0 g I2 = 1.0 g Total = 12.0 g 50 ml of water at 1000 A dissolves I1 dissolves I2 insoluble Solubility g/100 mL Compound 25o 100o A 1.0 80 I1 1.5 50 I2 0.0 0.0 A = 10 g I1 = 1.0 g I2 = 1.0 g Total = 12.0 g

o 50 mL water at 1000 Cool to 25

A dissolves A 9.5 g crystallize

I1 dissolves I1 0.25 g crystallize I2 insoluble Yield = 100 * 9.75/12.0 = 81% NOT PURE! What volume of solvent is needed to give the maximum yield of pure A?

Solubility of I1 = 1.5 g/100 mL

1.5 g 1.0 g = 100 mL x mL

X = (100 mL * 1.0 g)/1.5 g = 67 mL What is the yield of pure A from 67 mL solvent?

Solubility of A = 1.0 g/100 mL 1.0 g X g = 100 mL 67 mL

X = (67 mL x 1.0 g) / 100 mL = 0.67 g

Yield = 10.0 g - 0.67 g = 9.33 g

% yield = 100 * 9.33 / 12 = 78%

Boiling Points - Distillations

Ethylene glycol,

HOCH2CH2OH, boils at 198oC and melts at -13o C.

What happens to the melting point of water if you add antifreeze?

Melting point goes down. What happens to the boiling point of water if you add antifreeze?

The boiling point goes up. Mixtures

Solids Usually melt low

Usually boil Liquids between the two components Vapor pressure of water vs. temperature

Solution boils when the vapor pressure = applied pressure If you add salt, NaCl, to water what happens to the melting point?

Impurities depress the melting point so it goes down. If you add salt, NaCl, to water what happens to the boiling point?

The boiling point goes up. Raoult’s Law

o

Observed Mole Fraction Pressure Pure Substance Two Volatile Liquids

O

CH3 C CH3 Acetone Benzene b.p = 56o b.p. = 80o Two Volatile Liquids

o Pa = P a * Naa o Pb = P b * Nbb

Mixture boils when

Pa + Pb = Papplied Plot of boiling point vs. mole fraction for a mixture of acetone and benzene. Boiling point of an acetone-benzene mixture with a mole fraction benzene of 0.50

What is the composition of the vapor? Vapor richer in the lower boiling component Fractional Distillation

Packed Column

HETP = 1.5 cm Vigreux Column

HETP = 10 cm Experiment Separate mixture of methanol and water. Plot volume distilled vs. temperature.

CH OH 3 H2O methyl alcohol water methanol o b.p. = 64.7o b.p. = 100

CH3OH

Methyl alcohol is toxic! Standard Taper Joints 14/20

14 mm

20 mm Grease joints to prevent sticking.

Plug the thermowell into the variable transformer Put boiling chips in bottom of flask

Boiling Chips

Thermometer Adapter Water out

Water in

IDEAL MIXTURES:

Same interactions between like and unlike molecules

NONIDEAL MIXTURES:

A. Strong attractions between like molecules B. Strong attractions between unlike molecules Ethanol - Benzene Minimum - boiling azeotrope

Acetone - Chloroform

Maximum-boiling azeotrope

Simple Distillation

Extractions

Mixture of benzoic acid, anthracene, and p-nitroaniline O COH

NH2

NO2 Mixture of methylene chloride and water

Density of CH2Cl2 is 1.33 g/mL

H2O

CH2Cl2 If we dissolve NaCl in this mixture which phase has the highest salt concentration?

Salts concentrate in the water layer If we dissolve benzoic acid in this mixture in which phase would it concentrate?

Neutral organic compounds concentrate in Salts the organic phase Salts in water phase

Water

Neutral organic CH2Cl2 compounds in the organic phase Treatment of benzoic acid with sodium hydroxide converts it into the salt, sodium benzoate.

COOH + Na OH COO Na

Benzoic Acid Sodium Benzoate COOH + Na OH COO Na + - NH3 + HCl NH4 Cl Base Acid Salt O2NNH2 + HCl O2N NH3 Cl Use separatory funnel for separations. Shake to be sure phases equilibrate

Hold stopper and stopcock

benzoic Acid p-nitroaniline anthracene

HCl CH2Cl2

Benzoic acid O2N NH3 Cl Anthracene benzoic Acid anthracene

NaOH CH2Cl2

anthracene COO Na COO Na O2N NH3 Cl

HCl NaOH Dry filter

O2N NH2 COOH evaporate

Filter Filter weigh wash wash dry dry weigh weigh Addition of acid to the sodium benzoate solution causes benzoic acid to precipitate. The benzoic acid is filtered, washed, and dried. Weigh the benzoic acid and measure its melting point. NaOH O N NH O2N NH3 Cl 2 2

Cool to complete precipitation Dry the methylene chloride solution of anthracene with a small amount of sodium sulfate. Remove the drying agent by filtration through a fluted filter paper. Evaporate the methylene chloride on a steam bath. Use an inverted funnel connected to the vacuum line to collect the vapor. Weigh your products and measure their melting points.

Put your samples in labeled vials and give them to your TA. Partition Coefficients

10 g t-butyl alcohol 100 mL ether 100 mL water 10 grams t-butyl alcohol

x g / 200 mL 2.2 = ( 10 - x)g /100 mL

x = 8.1 grams Which is better?

Extract once with 200 mL or twice with 100 mL? If K = 1.0, a = 10 grams, S2 = 100 mL

Extract once with 200 mL yields 6.7 grams

Extract once with 100 mL yields 5.0 grams Second extraction with 100 mL yields 2.5 grams Total 2 extractions with 100 mL = 7.5 grams Grams extracted vs. number of extractions for K = 1, 2 and 4 Preparation of t-butyl chloride (2-chloro-2-methylpropane)

CH3 HCl CH3 CH3 C OH CH3 C Cl + H2O CH3 CH3 t-butyl alcohol t-butyl chloride (CH3)3COH + HCl

(CH3)3CCl + H2O

Reaction Mechanism? (CH3)3COH + H-Cl

+ - (CH3)3COH2 + Cl

Leaving Group + (CH3)3C-OH2

+ (CH3)3C H2O

Cation + - (CH3)3C + Cl

(CH3)3CCl tert-Butyl Cation + sp2 flat CH3 C CH3 CH3 p

Transition State

δ δ 2

1 bond Substitution at a time

Nucleophilic Increasing Stability Main Reaction

CH3 HCl CH3 CH3 C OH CH3 C Cl + H2O CH3 CH3 t-butyl alcohol t-butyl chloride

Side Reaction

CH3 HCl CH3 + H O CH3 C OH C CH2 2 CH 3 CH3 t-butyl alcohol isobutylene CH3

C

CH3 CH3

E1 N

CH3 CH3 C CH2 CH3 C Cl CH3 CH3 Procedure

Shake t-BuOH with concentrated HCl

Separate layers

Wash saturated aqueous NaCl

Wash saturated aqueous NaHCO3 Dry

Distill Shake t-BuOH with HCl

t-BuCl Wash to remove excess HCl

NaHCO3 + HCl

CO2 + H2O + NaCl Distill product

Cool receiver Clamp joints Yield Calculations

A + B C MW 100 100 200

Use: 10 g A 20 g B

Limiting Reagent Theoretical Yield Experimental Yield A + B C MW 100 100 200 Cpd Mass MW Moles Limiting A 10 g 100 0.10 Reagent B 20 g 100 0.20

Theoretical yield: 0.10 moles x 200 = 20 g Experimental yield (%): 100 x wt product / 20 HBr CH3CH2CH2CH2OH n-butyl alcohol

CH3CH2CH2CH2Br n-butyl bromide + + RCH2OH + H RCH2OH2

R δ− δ+ Br C OH2 H H transition state

RCH2Br

2 bonds at Substitution a time

Nucleophilic Methyl Benzoate

O

C OCH3 Esterification

O H2SO4 C OH + CH3OH Methanol Benzoic acid

O

C OCH3 + H2O

Methyl benzoate H+ O OH CH3 O C H -C C6H5-C 6 5 H OH OH

OH OH OH CH3 C6H5-C-O C6H5-C-OCH3 C6H5-C-OCH3 H OH OH O H H

OH O C H -C + 6 5 C6H5-C H OCH3 OCH 3 Resonance Stabilized Ion

OH OH C C OH OH

OH C OH Intermediate OH

C6H5-C-OCH3 OH

O O

C6H5COH C6H5COCH3 Reflux the mixture for 60 minutes.

Methanol Benzoic Acid Sulfuric Acid Boiling chips Equilibrium

O O H2SO4 C OH + CH3OH C OCH3 + H2O

[C6H5COOCH3][H2O] K = [C6H5COOH][CH3OH] Measure Equilibrium Constant

O O H2SO4 C OH + CH3OH C OCH3 + H2O

Recover benzoic Isolate and purifiy acid at equilibrium methyl benzoate C6H5COOH CH3OH H2SO4

Reflux, Cool, Extract with

CH2Cl2, H2O

CH2Cl2 H2O

C6H5COOCH3 H2SO4 C6H5COOH C6H5COOCH3 C6H5COOH

Extract with

NaHCO3 CH Cl 2 2 H2O

- + C6H5COOCH 3 C6H5COO Na C6H5COOCH 3

Dry Filter Distill Weigh

Methyl benzoate product Simple Distillation - + C6H5COO Na

HCl

C6H5COOH

Filter Wash Dry Weigh mp Benzoic Acid Product Calculate K

O O H2SO4 C OH + CH3OH C OCH3 + H2O

[C6H5COOCH3][H2O] K = [C6H5COOH][CH3OH]

Initial benzoic acid = Ao

Initial Methanol = Mo Recovered benzoic acid = A O O H2SO4 C OH + CH3OH C OCH3 + H2O

Initial: Ao Mo Equ: xx Ao - x Mo - x

X = Ao - A(recovered) [x][x] K = [Ao - x][Mo - x] Example

O O H2SO4 C OH + CH3OH C OCH3 + H2O

Ao = 0.100 moles Mo = 0.500 moles

A(Recovered) = 0.010 moles x = 0.100 - 0.010 = 0.090 moles

[0.090][0.090] K = = 1.7 [0.100 - 0.090][0.500 - 0.090] Nitration of Methyl Benzoate

COOH COOCH3 CH3OH

H2SO4

COOCH3 COOCH3

HNO3, H2SO4

NO2 Multistep Synthesis

50% 50% A B C

Yield = 25% Nucleophilic Aliphatic Substitution

HCl (CH3)3COH (CH3)3Cl

Electrophilic Aromatic Substitution

H NO2 + NO2 + ARENE SUBSTITUTION

H E E+ + H+

The electrophile REPLACES H+ H E - Y H E + H E - Y H E +

H E H E H E + +

+ E

+ H+ H E H E H E

+ +

+

Nitration of Benzene

NO2 HNO3

H2SO4 Nitrobenzene Nitration Reagent

+ + - HONO2 + 2 H2SO4 NO2 + H3O + 2 HSO4

Nitronium Ion H + H NO2 NO2 +

NO2

+ H+ Multiple Substituents

G

G G

G

Second Group. Where go? How fast? Nitration of Toluene

CH3 HNO3

CH CH3 CH3 3 NO2

NO2 NO2 63% 3% 34% ORTHO CH3 CH3 CH3 NO2 NO2 NO2 + H H H ++

META CH 3 CH3 CH3 + + NO2 NO2 NO2 H + H H

PARA CH CH3 3 CH3 + + +

H NO2 H NO2 H NO2 Electron donating groups favor reaction ORTHO and PARA.

Electron Donating

G Ortho

Para Nitration of (trifluoromethyl)benzene

CF3

HNO3

H2SO4

CF3 CF3 CF3

NO2

NO2 NO2 6% 91% 3% Electron Withdrawing group

CF3 + charge here bad Ortho CF 3 CF3 CF3 H H H + NO 2 NO NO2 ++2

Meta CF 3 CF3 CF3 + + H H H NO2 NO + NO2 2

CF Para 3 CF3 CF3 + + + H H NO2 NO2 H NO2 Electron Withdrawing Groups are Meta Directors and DEACTIVATING

Electron Withdrawing Z Group

Meta Product Main Reaction

COOCH3 COOCH3 HNO3, H2SO4 meta

NO2

Side Products

COOCH3 COOCH3 COOCH3 NO2

O2N NO2 NO2 Procedure

1. Dissolve methyl

benzoate in H2SO4

2. Mix HNO3 and o H2SO4 at 0 C

3. Add HNO3 / H2SO4 dropwise to methyl benzoate at 0oC 4. Let stand at room temperature 10 minutes

5. Pour onto ice Filter Wash

Recrystallize from methanol

Dry

Weigh m.p. Dehydration of Alcohols

H SO OH 2 4 + H2O H cyclohexanol cyclohexene Elimination Reactions

Y C - C X

To make C=C need to eliminate X, Y. Y C - C X 3 ways to break 2 bonds

1. Concerted (x and y leave same time) 2. X leaves first 3. Y leaves first Leaving Group

+ OH H2SO4 OH2 C C C C H H

+ OH2 + C C C C H H + C C C C H base

R-X R+ + X-

Alkene + H+ Elimination 1 bond at a time +

SN1 E1

Substitution Rearrangement Elimination CH3

C

CH3 CH3

E1 N

CH3 CH3 C CH2 CH3 C Cl CH3 CH3 Dehydrohalogenation

X C - C H Strong base What is the mechanism of dehydrohalogentation?

X X C - C C - C

H D

C-D bond stronger than C-H bond. Isotope Effect

H NaOEt C-CH2Br CH=CH2 H

D NaOEt CD=CH C-CH2Br 2 D

kH/kD = 7 Isotope effect shows that C-H bond broken in the transition state. Element Effect

X Change Element C - C H SYN vs. ANTI Elimination

H X X C - C C - C H Same Side Opposite Side H H

CH CH3 C H 3 C6H5 Br 6 5 H C6H5 H Br C6H5

CH3 C6H5

H C6H5

Transition State

Energy

Starting Material Product 2 Bonds at Elimination a time Procedure

H SO OH 2 4 + H2O H cyclohexanol cyclohexene • Put cyclohexanol and sulfuric acid in round bottom flask

• Fractional Distillation (steam distillation) collect distillate 80-85o

• Dry product with K2CO3

4. Distill Distil immiscible liquids

PT = PA + PB

(Steam Distillation) Baeyer Unsaturation Tests

Potassium Permanganate

KMnO4 - H2O R2C=CR2 + MnO4 alkene purple

OH OH

R2C - CR2 + MnO2 glycol dark brown Br2

Br

Br Br Br Bromine and Cyclohexene

Anisalacetophenone O O

CH3O CH + CH3C

Anisaldehyde Acetophenone

CH3O

NaO H H C C O H C

trans-anisalacetophenone Nucleophilic Aliphatic Substitution RX + Y- RY + X-

Esterification

ArCOOH + ROH ArCOOR + H 2O

Electrophilic Aromatic Substitution

HNO3 ArH ArNO2 H2SO4

Aldol Condensation Make new C-C bond O Acidic Hydrogen R-C O H Carboxylic Acid O R-C C H

Acidic Hydrogen O O

R-C R-C O O

O O R-C R-C C C Polar Carbonyl Group

- O O + C C Nucleophilic Addition to Carbonyl Group

- O O C C

- Y Y - O OH

CCH3 - O O - C CH2 C CH2 O

H C OCH3

- O O C CH2 C OCH3 H O OH C CH2 C OCH3 H

O

CCH CH OCH3 Side Reactions:

O - O

C CH2 + CH3 C

O OH C CH2 C CH3

O CCH C CH3 Cannizzaro Reaction - O O - CH O C H CH3O CH + OH 3 OH

- O O

CH3O C H C OCH3 OH H

O OH H C OCH3 CH3O C OH H Procedure

Get sample of acetophenone from storeroom

Locate p-anisaldehyde in hood

Measure sample of ansialdehyde Dissolve anisaldehyde and acetophenone in 95% ethanol

Dissolve NaOH in water

Mix and allow to stand for about 10 minutes Cool

Filter

Wash Recrystallize

Weigh

m.p. Identify an Unknown

Type of compound: Aldehyde Alcohol Amine Ketone Procedure

1. Physical Properties Melting point or boiling point

2. Functional Group Infrared spectrum NMR Spectrum Solubility Classification Tests

3. Solid Derivative Measure boiling point of liquids Functional Group Carbonyl Group (1650 - 1725 cm-1)?

Yes No Aldehyde Alcohol Ketone Amine Broad NMR OH in IR - + Yes No Aldehyde Ketone Alcohol Amine (Basic?) 3700 - 4000 cm-1

Yes No Primary or Secondary Tertiary 2,4-dinitrophenylhydrazine test

NH2NH NO2

NO2

Aldehyde or ketone 2,4-dinitrophenylhydrazone

O + R-C-R NH2NH NO2

NO2

R C NNH NO2 R NO2 O OH C NH2R C NHR

C NR Iodoform Test

Reagent: NaOH and I2 (NaOI)

O I2, NaOH RCCH3 RCOOH + CHI 3 Yellow Iodoform Test

O I2, NaOH RCCH3 RCOOH + CHI3 Yellow

OH I2, NaOH RCHCH3 RCOOH + CHI3 Yellow

Amines

1. Odor

2. If not soluble in water they may dissolve in dilute aqueous acid (HCl).

3. Water solutions of amines are basic to litmus. Hinsberg Test for Amines

SO2Cl

Benzenesulfonyl Chloride Hinsberg Test for Amines

Primary: Soluble. PPT if add HCl Secondary: Insoluble Tertiary: Tends not to react Derivatives Aldehydes and Ketones

1. 2,4-dinitrophenylhydrazone

2. Semicarbazone

O O O R NH2NHCNH2 + RC R C NNHCNH2 semicarbazide R semicarbazone Alcohol Derivative

O2N O2N O O ROH CCl C OR

O2N O2N

3,5-dinitrobenzoyl 3,5-dinitrobenzoate chloride Amine Derivatives Primary and Secondary Amines

O O

C Cl + RNH2 C NHR

Benzoyl Chloride Benzamide

SO2Cl + RNH2 SO2NHR

Benzenesulfonyl Chloride Benzenesulfamide Sample Unknown

B.p. =198-200o

DNP = 231-235o

O

C CH3 acetophenone Sample Unknown

B.p. = 80 - 85o

3,5-dinitrobenzoate = 119 - 121o

OH

CH3 C CH3 H isopropyl alcohol B.p = 106o

3,5-dinitrobenzoate 85o

CH3

CH CH2OH

CH3 isobutyl alcohol B.p. = 160o

3,5-dinitrobenzoate: 108-110o

H

OH cyclohexanol B.p. = 155-157o

2,4-DNP = 158 - 160o

O

cyclohexanone B.p. = 180 -183o

Benzenesulfonamide 110 - 112o Benzamide 160 - 163o

NH2

aniline Infrared Spectroscopy

Identify the functional group(s) Electromagnetic Spectrum Bond Vibrations

Energy absorption radiation

Amplitude H H C Stretching C H H

H H Bending C C H H Classical IR Spectrometer

NaClNaCl IRIR PlatesPlates

A drop of sample is place between the NaCl plates NaCl cell for solutions

Wavenumber cm-1 E = hν= hc/ λ Characteristic IR Absorption Frequencies Bond cm-1 C-H Alkanes 2850-2960 C-H Alkenes 3020-3080 C-H Arenes 3000-3100

C-O Alcohols, ethers 1080-1300

C=O Aldehydes, ketones... 1690-1760

O-H Alcohols 3200-3600 Acids 2500-3000

N-H Amines 3300-3500 -OH Alcohol

C-H

-O-R PrimaryAmine

-NH2 N-H C=O Aldehyde

RCO-H

C=O Carboxylic Acid

OH C=O C-O C=O Functional Group?

Carbonyl group -- Ketone Functional Group?

Alcohol Functional Group?

Carboxylic Acid Functional Group?

Ester Functional Group?

amine (secondary) C8H8O

C6H5COCH3 C3H8O

isopropyl alcohol C4H8O2

CH3COOCH2CH3 C5H10O

CH3COCH2CH2CH3 Nuclear Magnetic Resonance

Chapter 13 Proton Nuclear Spin States

Magnetic Field

Two states have the same energy in the absence of a magnetic field Protons in an external magnetic field

Energy difference between the spin-states depends on the strength of the magnetic field. NMR Spectrometer Superconducting NMR Magnet NMR Sample Tubes NMR Probe

Sample goes Coils in here Insulated tube

Proton NMR Spectrum of Cl3CH

NMR Signal

Magnetic Field Field here less than Ho

H

Ho Electrons shield nucleus from external magnetic field.

Magnetic field Energy to change spin state proportional to field strength

E =γ H E =hν

Measure field strength in FREQUENCY units Cycles/second Tetramethylsilane

CH3

CH3 Si CH3

CH3 TMS

Reference compound for NMR spectrum. Cl3CH

NMR 437 Hz signal at 60x106 Hz

TMS

Magnetic Field δ Chemical Shift Scale

Position of Signal - Position of TMS Chemical Shift = x106 Spectrometer Frequency

437 Hz - 0 Hz δ = x 106 = 7.28 ppm 60x106Hz

Units = parts per million = ppm Typical Chemical Shifts

R C H 0.9 - 1.8

Br C H 2.7 - 4.1 O C C H 2.1 - 2.5

O C H 3.3 - 3.7

Cl C H 3.1 - 4.1 Typical Chemical Shifts

C H 2.3 - 2.8 O C H 9 - 10

H C C 4.5 - 6.5

R O H 0.5 - 5

H 6.5 - 8.5 Proton Chemical Shifts

H O O X C C = C H C-C-H RH TMS C H H

10 9 8 7 6 5 4 3 2 1 0

ppm down field from TMS

Area proportional to number of protons How many lines would you expect in the proton NMR spectrum of this compound?

C C X

H H Field from this proton Measure signal can be aligned or from this proton opposed to applied field

Magnetic Field Spin Combinations - 2 adjacent protons

-C-CH2- H

1 : 2 : 1 Spin Combinations - 3 Adjacent Protons

-C-CH3 H

1: 3: 3: 1 Adjacent Protons Lines 1 2 2 3 3 4

What is the name of this compound?

Ethyl Bromide

O

CH3C OCH2CH3

ICH2CH2CH3

What is this compound?

CH3COCH2CH3 What is this compound?

C6H5COCH3 What is this compound?

C6H5COOCH2CH3 Magnetic field changes across sample y

x 13

Common nuclei which have a magnetic moment:

1H 13C 15N 19F (Odd mass number or even mass number and odd atomic number) Only 1.1% of the carbon atoms in a sample are C13

C12 does not have a magnetic moment. C13 NMR H H H 13 H C C C H H H H Signal weak No C-C coupling Strong C-H coupling Large Chemical Shifts C13 Chemical Shifts ppm from TMS

C C 65 - 90 RCH3 0 - 35

R2CH2 15 -40 C C 100 - 150

R3CH 25 - 50 110 - 175

RCH2Cl 25 - 50

C O 190 - 220 Proton NMR Spectrum O

CH3CH2COCH2CH3 Carbon NMR Spectrum (Proton Decoupled) O

CH3CH2COCH2CH3 Peak height (area) NOT proportional to number of C atoms. OH

CH3CHCH2CH3 Proton decoupled CMR Proton coupled CMR