Chemistry 234Organic Chemistry Laboratory

Stan Smith

sg-smith@uiuc.edu

www.chem.uiuc.edu

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2 points/lesson

Due May 2, 2001

Laboratory NotebookReference

Data

Observations

Properties:

compoundssolvents

Laboratory Reports

Safety EquipmentEye 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

GradesLaboratory Reports

2 50 minute Exams

On-line Quizzes

ChemNet

15% A 30% B 50% C 5% D + E

230

2x100 = 200

10*10 = 100

16*2 = 36

Hour Exam Dates

Exam 1: Thursday, March 1, 2001

Exam 2: Wednesday, April 25, 2001

Dates:

Time: 7:00 p.m.

Breakage Replacement Card

Change Section - Makeup Labs

Mike Eubanks469 Noyes Lab

Melting Points and Mixed Melting PointsExperiment 1: Identify a compound by its meltingpoint and mixed melting points.

Acetamide

p-Aminobenzoic acid

Camphoric Acid

trans-Cinnamic Acid

Malonic Acid

p-Nitrophenol

Resorcinol

Succinic Acid

Urea

113 - 115 oC

188 - 189 oC

183 - 186 oC

133 - 134 oC

135 - 137 oC

113 - 115 oC

110 - 113 oC

187 - 189 oC

133 - 135 oC

A sample is putin the bottom ofa melting pointtube.

Put a small amount of the compound in theopen end of the melting point tube.

Turn over and tape the closed end on the desktop until the compound falls to the bottom.

Sample in themelting pointtube.

Use a Thiele tube filled withmineral oil to heat your sample.

Attach the melting point tubeto a thermometer.

Heat about 5o per minuteuntil within about 10o ofthe melting point

Near the melting pointheat at 1 - 2o perminute

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 themelting point if saltis added?

Ice melts!

Impurities such as salt lowers the meltingpoint of water.

Putting salt on icy roads causes the ice tomelt because it lowers the melting point ofwater.

Impure compounds usually melt lower thanpure compounds so the melting point maybe used as a measure of the purity of acompound

Acetic Acid, CH3COOH,is a colorless liquid thatmelts at 16.6oC.

Let’s look at the melting point ofmixtures of water and acetic acid.

Plot of melting point vs. mole fraction waterfor mixtures of water and acetic acid.

Eutectic point

Cool a acetic acid - water solutionwith a mole fraction water of 0.9

Heat a acetic acid - water solutionwith a mole fraction water of 0.9

Heat a acetic acid - water solutionwith a mole fraction water of 0.2

Pure compounds usually melt overa narrow temperature range, often1o or less.

Impure compounds melt lowerthan pure compounds and over awider temperature range.

m.p. = 115o - 119o m.p. = 118o - 120o m.p. = 121o - 122o

Melting points are a measure of purity

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

Two of these bottles contain benzoicacid and one m-nitrophenylacetic acid.

How do you tell what is in each bottle?

Mixed Melting Points

Grind samples together to be sure they aremixed and then measure the melting point.

m.p. = 114o - 117o

m.p. = 120o - 122o

m.p. = 115o - 118o

Mixed 1 and 2

Mixed 1 and 3

Mixed 2 and 3

1 2 3

Results

1. Measure the melting pointof your unknown

2. Run mixed melting pointsto confirm identification

Recrystallization

Impure benzoicacid

Benzoic acid afterrecrystallization

C-OH

O

Benzoic Acid

m.p. = 121 - 122o

Purification of Organic Compounds

Solids: Recrystallization

Liquids: Distillation

Solids and Liquids:

Gas or liquid chromotography

Types of impuritiesSoluble

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 allsoluble material dissolves

Insoluble material is removed by filtration

The hot solution is filtered toremove insoluble impurities

Use fluted filter paper tomaximize surface area.

To avoidcrystallizationin the funnel:

Use GLASS funnel.Put flask on hot plate.

Boil off excess solvent

Boiling Sticks

Hot solutionafter filtration:

Cool Seed Scratch

Crystals form in the warm solution

Next:

Cool, filter, wash, dry, weigh, mp

Buchner funnel..

Filter flask

Heavy-walledtubing

Vacuum

Put filter paper in Buchner funnel..

Filter and wash with cold solvent

Insoluble impurities

Solubleimpurities

Purifiedbenzoic acid

Solubility Example

Compound Solubility g/100 mL

25o 100o

A

I1

I2

1.0

1.5

0.0

80

50

0.0

CompoundSolubility g/100 mL

25o 100o

A

I1

I2

1.0

1.5

0.0

80

50

0.0

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

100 mL water at 1000

A

I1

I2

dissolves

dissolves

insoluble

CompoundSolubility g/100 mL

25o 100o

A

I1

I2

1.0

1.5

0.0

80

50

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

Cool to 25o

A

I1

9.0 g crystallize

0 g crystallize

Yield = 100 * 9.0/12.0 = 75%

CompoundSolubility g/100 mL

25o 100o

A

I1

I2

1.0

1.5

0.0

80

50

0.0

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

50 ml of water at 1000

A

I1

I2

dissolves

dissolves

insoluble

CompoundSolubility g/100 mL

25o 100o

A

I1

I2

1.0

1.5

0.0

80

50

0.0

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

50 mL water at 1000

A dissolves

I1 dissolves

I2 insoluble

Cool to 25o

A

I1

9.5 g crystallize

0.25 g crystallize

Yield = 100 * 9.75/12.0 = 81%

NOT PURE!

What volume of solvent is needed togive the maximum yield of pure A?

Solubility of I1 = 1.5 g/100 mL

1.5 g100 mL = 1.0 g

x mL

X = (100 mL * 1.0 g)/1.5 g = 67 mL

What is the yield of pure A from 67 mLsolvent?

Solubility of A = 1.0 g/100 mL

1.0 g100 mL = X g

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 at198oC and melts at -13o C.

What happens to the meltingpoint of water if you addantifreeze?

Melting point goes down.

What happens to theboiling point of water ifyou add antifreeze?

The boiling point goes up.

Mixtures

Solids Usually melt low

LiquidsUsually boilbetween the twocomponents

Vapor pressure of water vs. temperature

Solution boils when the vapor pressure =applied pressure

If you add salt, NaCl,to water what happensto the melting point?

Impurities depressthe melting point soit goes down.

If you add salt, NaCl,to water what happensto the boiling point?

The boiling pointgoes up.

Raoult’s Law

o

ObservedPressure

Pure Substance

Mole Fraction

C

O

CH3CH3

Acetoneb.p = 56o Benzene

b.p. = 80o

Two Volatile Liquids

Two Volatile LiquidsPa = Po

a * Naa

Pb = Pob * Nbb

Mixture boils when

Pa + Pb = Papplied

Plot of boiling point vs. mole fractionfor a mixture of acetone and benzene.

Boiling point of an acetone-benzene mixturewith 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

CH3OHmethyl alcoholmethanolb.p. = 64.7o

H2Owaterb.p. = 100o

ExperimentSeparate mixture of methanol and water.Plot volume distilled vs. temperature.

CH3OH

Methyl alcohol is toxic!

Standard Taper Joints

14/20

20 mm

14 mm

Grease joints toprevent sticking.

Plug the thermowell into thevariable transformer

Put boiling chips in bottom of flask

Boiling Chips

ThermometerAdapter

Water in

Water out

IDEAL MIXTURES:

Same interactions between likeand unlike molecules

NONIDEAL MIXTURES:

Strong attractions between likemoleculesStrong attractions between unlikemolecules

A.

B.

Ethanol - Benzene

Minimum - boiling azeotrope

Acetone - Chloroform

Maximum-boiling azeotrope

Simple Distillation

Extractions

Mixture of benzoic acid, anthracene, andp-nitroaniline

COHO

NH2

NO2

Mixture of methylene chloride and water

Density of CH2Cl2 is 1.33 g/mL

CH2Cl2

H2O

If we dissolve NaCl in this mixturewhich phase has the highest saltconcentration?

Salts concentrate inthe water layer

If we dissolve benzoic acid in thismixture in which phase would itconcentrate?

Neutral organiccompounds concentrate inthe organic phase

Salts

Salts in water phase

Neutral organiccompounds in theorganic phase

Water

CH2Cl2

COOH + Na OH COO Na

Benzoic Acid Sodium Benzoate

Treatment of benzoic acid withsodium hydroxide converts itinto the salt, sodium benzoate.

COOH + Na OH COO Na

NH3 + HCl NH4+ Cl-

Base Acid Salt

NH2O2N + HCl NH3O2N Cl

Use separatory funnel for separations.

Shake to be surephases equilibrate

Hold stopperand stopcock

benzoic Acid

p-nitroaniline

anthracene

HCl CH2Cl2

NH3O2N ClBenzoic acid

Anthracene

benzoic Acid

anthracene

NaOH CH2Cl2

COO Na anthracene

NH3O2N Cl COO Na

NH2O2N

NaOH

COOH

Filterwashdryweigh

HCl

Filterwashdryweigh

Dryfilterevaporate

weigh

Addition of acid tothe sodiumbenzoate solutioncauses benzoic acidto precipitate.

The benzoic acid isfiltered, washed,and dried.

Weigh the benzoicacid and measure itsmelting point.

NH2O2NNH3O2N ClNaOH

Cool to complete precipitation

Dry the methylene chloride solutionof anthracene with a small amountof sodium sulfate.

Remove the drying agent by filtrationthrough a fluted filter paper.

Evaporate themethylene chlorideon a steam bath.

Use an invertedfunnel connected tothe vacuum line tocollect the vapor.

Weigh your products and measuretheir melting points.

Put your samples in labeled vialsand give them to your TA.

10 g t-butyl alcohol100 mL ether100 mL water

Partition Coefficients

2.2 = x g / 200 mL

( 10 - x)g /100 mL

x = 8.1 grams

10 grams t-butyl alcohol

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 gramsSecond extraction with 100 mL yields 2.5 gramsTotal 2 extractions with 100 mL = 7.5 grams

Grams extracted vs. number of extractionsfor K = 1, 2 and 4

Preparation of t-butyl chloride(2-chloro-2-methylpropane)

CCH3

CH3CH3

OHHCl

CCH3

CH3CH3

Cl + H2O

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

C CH3

CH3

CH3

tert-Butyl Cation

+sp2 flat

p

2

Transition State

δ δ

Substitution

Nucleophilic

1 bondat a time

Increasing Stability

Main Reaction

Side Reaction

CCH3

CH3CH3

OHHCl

CCH3

CH3CH3

Cl + H2O

t-butyl alcohol t-butyl chloride

CCH3

CH3CH3

OHHCl

+ H2O

t-butyl alcohol

CH2CCH3

CH3

isobutylene

CH2CCH3

CH3

C

CH3

CH3CH3

CCH3

CH3CH3

Cl

E1 N

ProcedureShake t-BuOH with concentrated HCl

Separate layers

Wash saturated aqueous NaCl

Wash saturated aqueous NaHCO3

Dry

Distill

t-BuCl

Shake t-BuOH with HCl

NaHCO3 + HCl

CO2 + H2O + NaCl

Wash to remove excess HCl

Distill product

Cool receiver

Clamp joints

Yield Calculations

A + B CMW 100 100 200

Use: 10 g A 20 g B

Limiting Reagent

Theoretical Yield

Experimental Yield

A + B CMW 100 100 200

Cpd Mass MW Moles

A 10 g 100 0.10

B 20 g 100 0.20

Theoretical yield:0.10 moles x 200 = 20 g

Experimental yield (%):100 x wt product / 20

LimitingReagent

CH3CH2CH2CH2OH n-butyl alcohol

HBr

CH3CH2CH2CH2Brn-butyl bromide

RCH2OH + H+ RCH2OH2+

C

R

HHOH2Br

δ− δ+

transition state

RCH2Br

Substitution

Nucleophilic

2 bonds ata time

Methyl Benzoate

CO

OCH3

CO

OH + CH3OHH2SO4

Esterification

Benzoic acidMethanol

Methyl benzoate

CO

OCH3 + H2O

C6H5-COH

OH+

C6H5-C

OH

OH

OCH3

H

C6H5-C-O

OH

OH

CH3

HC6H5-C-OCH3

OH

OH

C6H5-C-OCH3

OH

OHH

C6H5-COH

OCH3C6H5-C

OCH 3

OH+

COH

OHC

OH

OH

COH

OH

Resonance Stabilized Ion

C6H5-C-OCH3

OH

OH

Intermediate

COH

O

C6H5 COCH3

O

C6H5

Reflux the mixturefor 60 minutes.

Methanol

Benzoic Acid

Sulfuric Acid

Boiling chips

CO

OCH3CO

OH + CH3OHH2SO4

+ H2O

Equilibrium

K = [C6H5COOCH3][H2O]

[C6H5COOH][CH3OH]

CO

OCH3CO

OH + CH3OHH2SO4

+ H2O

Measure Equilibrium Constant

Recover benzoicacid at equilibrium

Isolate and purifiymethyl benzoate

C6H5COOH CH3OH H2SO4

Reflux, Cool,Extract withCH2Cl2, H2O

CH2Cl2 H2O

H2SO4C6H5COOCH3C6H5COOH

C6H5COOCH3C6H5COOH

Extract withNaHCO3

CH2Cl2 H2O

C6H5COOCH 3 C6H5COO Na- +

C6H5COOCH 3

Dry

Filter

Distill

Weigh

Methyl benzoate product

Simple Distillation

C6H5COO Na- +

HCl

C6H5COOH

FilterWashDryWeighmp

Benzoic Acid Product

CO

OCH3CO

OH + CH3OHH2SO4

+ H2O

K = [C6H5COOCH3][H2O]

[C6H5COOH][CH3OH]

Calculate K

Initial benzoic acid = Ao

Initial Methanol = Mo

Recovered benzoic acid = A

CO

OCH3CO

OH + CH3OHH2SO4

+ H2O

Initial: Ao Mo

Equ: Ao - x Mo - x x x

X = Ao - A(recovered)

K =[x][x]

[Ao - x][Mo - x]

CO

OCH3CO

OH + CH3OHH2SO4

+ H2O

Example

Ao = 0.100 moles Mo = 0.500 moles

A(Recovered) = 0.010 moles

x = 0.100 - 0.010 = 0.090 moles

K = [0.090][0.090][0.100 - 0.090][0.500 - 0.090] = 1.7

Nitration of Methyl Benzoate

COOCH3

HNO3, H2SO4

COOCH3

NO2

COOCH3COOHCH3OH

H2SO4

Multistep Synthesis

A B C50% 50%

Yield = 25%

(CH3)3COH (CH3)3ClHCl

Nucleophilic Aliphatic Substitution

NO2+

+

H NO2

Electrophilic Aromatic Substitution

ARENE SUBSTITUTION

H EE+

+ 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 BenzeneNO2

HNO3

H2SO4

Nitrobenzene

Nitration Reagent

Nitronium Ion

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

-

HNO2

+ H NO2

+

NO2

+ H+

Multiple SubstituentsG

G G

G

Second Group. Where go? How fast?

Nitration of TolueneCH3

CH3NO2

CH3

NO2

CH3

NO2

HNO3

63% 3% 34%

CH3NO2

H

CH3NO2

H

CH3NO2

H+

+ +

CH3

NO2

H

CH3

NO2

H

CH3

NO2

H

CH3

NO2H

CH3

NO2H

CH3

NO2H

+

+

+

+ ++

ORTHO

META

PARA

G

Electron donating groups favorreaction ORTHO and PARA.

Electron Donating

Ortho

Para

CF3

Nitration of (trifluoromethyl)benzene

HNO3

H2SO4

CF3

NO2

CF3

NO2

CF3

NO2

6% 91% 3%

CF3

Electron Withdrawing group

+ chargehere bad

CF3HNO2

CF3H

NO2

CF3H

NO2

CF3

H

NO2

CF3

H

NO2

CF3

H

NO2

CF3

H NO2

CF3

H NO2

CF3

H NO2

Ortho

Meta

Para

++ +

+

+

+

+ ++

Z

Electron Withdrawing Groups areMeta Directors and DEACTIVATING

ElectronWithdrawingGroup

Meta Product

COOCH3

HNO3, H2SO4

COOCH3

NO2

Main Reaction

Side Products

meta

COOCH3NO2

NO2

COOCH3 COOCH3

NO2O2N

Procedure

1. Dissolve methyl benzoate in H2SO4

2. Mix HNO3 and H2SO4 at 0oC

3. Add HNO3 / H2SO4 dropwise to methyl benzoate at 0oC

4. Let stand at roomtemperature 10minutes

5. Pour onto ice

Filter

Wash

Recrystallize frommethanol

Dry

Weigh

m.p.

Dehydration of Alcohols

OH

H+ H2O

H2SO4

cyclohexanol cyclohexene

Elimination Reactions

C - C

X

Y

To make C=C need to eliminate X, Y.

C - C

X

Y

3 ways to break 2 bonds1. Concerted (x and y leave same time)2. X leaves first3. Y leaves first

CC

H

OH H2SO4CC

H

OH2+

CC

H

OH2+

CC

H

+

Leaving Group

CC

H

+

base

CC

R-X R+ + X-

Alkene + H+

Elimination 1 bondat a time

+

Substitution

Elimination

Rearrangement

SN1E1

CH2CCH3

CH3

C

CH3

CH3CH3

CCH3

CH3CH3

Cl

E1 N

Dehydrohalogenation

C - C

X

H

Strong base

C - C

X

H

What is the mechanism of dehydrohalogentation?

C - C

X

D

C-D bond stronger than C-H bond.

C-CH2Br

H

H

CH=CH2

NaOEt

C-CH2Br

D

DNaOEt

CD=CH2

Isotope Effect

kH/kD = 7

Isotope effect shows thatC-H bond broken in thetransition state.

Element Effect

C - CX

H

Change Element

SYN vs. ANTI Elimination

C - CX

H

C - C

H X

Same Side Opposite Side

H

C6H5CH3C6H5H

Br

H

C6H5CH3Br

HC6H5

C6H5

C6H5

CH3

H

Transition State

Product

StartingMaterial

Energy

Elimination 2 Bonds ata time

OH

H+ H2O

H2SO4

cyclohexanol cyclohexene

Procedure

• Put cyclohexanol and sulfuric acid inround bottom flask

• Fractional Distillation (steamdistillation) collect distillate 80-85o

• Dry product with K2CO3

4. Distill

Distil immiscible liquids

PT = PA + PB

(Steam Distillation)

Baeyer Unsaturation Tests

PotassiumPermanganate

KMnO4

R2C=CR2 + MnO4- H2O

purplealkene

R2C - CR2

OH OH

+ MnO2

darkbrown

glycol

Br2

Br

Br

BrBr

Bromine and Cyclohexene

Anisalacetophenone

CH3O CHO

Anisaldehyde

+ CH3CO

Acetophenone

CCH C

H

CH3O

O

trans-anisalacetophenone

NaOH

Nucleophilic Aliphatic Substitution

RX + Y- RY + X-

EsterificationArCOOH + ROH ArCOOR + H 2O

Electrophilic Aromatic Substitution

ArH ArNO2HNO3

H2SO4

Aldol Condensation

Make new C-C bond

R-C OH

O

Carboxylic Acid

Acidic Hydrogen

R-C

O

C

H

Acidic Hydrogen

R-C

O

OR-C

O

O

R-C

O

C CR-C

O

C

OC

O -

+

Polar Carbonyl Group

C

O

C

O -

Y- Y

Nucleophilic Addition to Carbonyl Group

CCH3

O OH-

C CH2

O-

CO

CH2

-

OCH3CHO

C CH2

OCH

OOCH3

-

C CH2

OCH

OHOCH3

C CHO

CH OCH3

Side Reactions:

C

O

CH2

-+ CCH3

O

C CH2

OCCH3

OH

C CHO

CCH3

CH3O C HO

+ OH- CH3O C

OHH

O-

CH3O COH

HO-

OCH3CO

H

CCH3O OHO

OCH3CHH

OH

Cannizzaro Reaction

ProcedureGet sample of acetophenonefrom storeroom

Locate p-anisaldehyde inhood

Measure sample of ansialdehyde

Dissolve anisaldehyde andacetophenone in 95% ethanol

Dissolve NaOHin water

Mix and allow tostand for about10 minutes

Cool

Filter

Wash

Recrystallize

Weigh

m.p.

Type of compound:Aldehyde

Alcohol

Amine

Ketone

Identify an Unknown

Procedure

1. Physical PropertiesMelting point or boiling point

2. Functional Group

Infrared spectrum

NMR Spectrum

Solubility

Classification Tests

3. Solid Derivative

Measure boilingpoint of liquids

Functional GroupCarbonyl Group (1650 - 1725 cm-1)?

Yes No

AldehydeKetone

NMR

Aldehyde Ketone+ -

AlcoholAmine

BroadOH in IR

Yes NoAlcohol Amine

(Basic?)3700 - 4000 cm-1

YesPrimary or Secondary

NoTertiary

2,4-dinitrophenylhydrazine test

NH2NH

NO2

NO2

Aldehyde or ketone

R-C-R

O+ NH2NH

NO2

NO2

NNH

NO2

NO2CR

R

2,4-dinitrophenylhydrazone

C

ONH2R C

OH

NHR

NRC

Iodoform TestReagent: NaOH and I2 (NaOI)

CCH3

O

RI2, NaOH

RCOOH + CHI 3Yellow

CCH3

O

RI2, NaOH

RCOOH + CHI3Yellow

Iodoform Test

CHCH3

OH

RI2, NaOH

RCOOH + CHI3Yellow

Amines

1. Odor

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

3. Water solutions of amines arebasic to litmus.

Hinsberg Test for Amines

SO2Cl

Benzenesulfonyl Chloride

Hinsberg Test for Amines

Primary: Soluble. PPT if add HClSecondary: Insoluble

Tertiary: Tends not to react

DerivativesAldehydes and Ketones

1. 2,4-dinitrophenylhydrazone

2. Semicarbazone

NH2NHC

O

NH2

semicarbazide

+ RC

O

R NNHCNH2CR

RO

semicarbazone

Alcohol Derivative

O2N

O2N

C ClO

O2N

O2N

C OROROH

3,5-dinitrobenzoyl chloride

3,5-dinitrobenzoate

Amine DerivativesPrimary and Secondary Amines

CO

Cl + RNH2 CO

NHR

Benzoyl Chloride Benzamide

SO2Cl + RNH2 SO2NHR

Benzenesulfonyl Chloride Benzenesulfamide

Sample Unknown

B.p. =198-200o

DNP = 231-235o

C

O

CH3

acetophenone

Sample Unknown

B.p. = 80 - 85o

3,5-dinitrobenzoate= 119 - 121o

CCH3 CH3

H

OH

isopropyl alcohol

B.p = 106o

3,5-dinitrobenzoate85o

CH2OHCH

CH3

CH3

isobutyl alcohol

B.p. = 160o

3,5-dinitrobenzoate:108-110o

OH

H

cyclohexanol

B.p. = 155-157o

2,4-DNP = 158 -160o

O

cyclohexanone

B.p. = 180 -183o

Benzenesulfonamide110 - 112o

Benzamide 160 - 163o

NH2

aniline

Infrared Spectroscopy

Identify the functional group(s)

Electromagnetic Spectrum

Energy

Amplitude

absorption radiation

Bond Vibrations

CH

HC

H

HBending

CH

HC

H

HStretching

Classical IR Spectrometer

NaClNaCl IR Plates IR Plates

A drop of sample is place between the NaCl plates

NaCl cell for solutions

Wavenumber cm-1

E = h�= hc/ν λ

Characteristic IR Absorption Frequencies

C-H Alkanes 2850-2960C-H Alkenes 3020-3080C-H Arenes 3000-3100

C-O Alcohols, ethers 1080-1300

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

O-H Alcohols 3200-3600Acids 2500-3000

N-H Amines 3300-3500

cm-1Bond

-OH

C-H

-O-R

Alcohol

PrimaryAmine

-NH2

N-H

C=O

Aldehyde

C=O

RCO-H

Carboxylic Acid

OH

C=O

C=OC-O

Carbonyl group -- Ketone

Functional Group?

Alcohol

Functional Group?

Carboxylic Acid

Functional Group?

Ester

Functional Group?

amine (secondary)

Functional Group?

C6H5COCH3

C8H8O

isopropyl alcohol

C3H8O

CH3COOCH2CH3

C4H8O2

CH3COCH2CH2CH3

C5H10O

NuclearMagneticResonance

Chapter 13

Proton Nuclear Spin States

Two states have the same energyin the absence of a magnetic field

MagneticField

Protons in an external magnetic field

Energy difference between the spin-statesdepends on the strength of the magnetic field.

NMR Spectrometer

Superconducting NMR Magnet

NMR Sample Tubes

NMR Probe

Sample goesin here

CoilsInsulated tube

NMRSignal

Proton NMR Spectrum of Cl3CH

Magnetic Field

H

Ho

Field here less than Ho

Electrons shield nucleus fromexternal magnetic field.

Magnetic field

E = H

Energy to change spin stateproportional to field strength

E =h

Measure field strength in FREQUENCYunits

Cycles/second

γ

ν

Si CH3

CH3

CH3

CH3

Tetramethylsilane

TMSReference compound for NMR spectrum.

NMRsignal

Magnetic Field

Cl3CH

TMS

437 Hzat 60x106 Hz

Chemical Shift =Position of Signal - Position of TMS

Spectrometer Frequencyx106

Units = parts per million = ppm

Chemical Shift Scale

=437 Hz - 0 Hz60x106Hz

x 106 = 7.28 ppmδ

δ

Typical Chemical Shifts

CR H

CO

C H

CCl H

CBr H

CO H

0.9 - 1.8

2.1 - 2.5

3.1 - 4.1

2.7 - 4.1

3.3 - 3.7

C H

CCH

H

CO

H

HOR

Typical Chemical Shifts

2.3 - 2.8

4.5 - 6.5

6.5 - 8.5

9 - 10

0.5 - 5

10 9 8 7 6 5 4 3 2 1 0

TMSRHC-C-HO

C HXC = CH

H

C H

O

Proton Chemical Shifts

ppm down field from TMS

Area proportional to number of protons

How many lines would youexpect in the proton NMRspectrum of this compound?

C C

H H

X

Measure signalfrom this proton

Field from this protoncan be aligned oropposed to appliedfield

Magnetic Field

Spin Combinations - 2 adjacent protons

-C-CH2-H

1 : 2 : 1

Spin Combinations - 3 AdjacentProtons

-C-CH3

H

1: 3: 3: 1

Adjacent Protons Lines

123

234

What is the name of this compound?

Ethyl Bromide

CH3CO

OCH2CH3

ICH2CH2CH3

What is this compound?

CH3COCH2CH3

C6H5COCH3

What is this compound?

What is this compound?

C6H5COOCH2CH3

y

x

Magneticfield changesacross sample

13Common nuclei which have a magnetic moment:

1H13C15N19F

(Odd mass number or even mass number and odd atomic number)

Only 1.1% of the carbonatoms in a sample are C13

C12 does not have a magneticmoment.

CCC HH

H

H

HH

H

H

13

Signal weakNo C-C couplingStrong C-H couplingLarge Chemical Shifts

C13 NMR

C13 Chemical Shifts

RCH3

R2CH2

RCH2Cl

R3CH

CC

CC

OC

0 - 35

15 -40

25 - 50

25 - 50

65 - 90

100 - 150

110 - 175

190 - 220

ppm from TMS

COCH2CH3

OCH3CH2

Proton NMR Spectrum

Carbon NMR Spectrum

COCH2CH3

OCH3CH2

(Proton Decoupled)

CHCH2CH3

OHCH3

Peak height (area) NOT proportionalto number of C atoms.

Proton decoupled CMR

Proton coupled CMR