15-1 Chemistry 121, Winter 2011, LA Tech Introduction to Organic Chemistry and Biochemistry...

15-1Chemistry 121, Winter 2011, LA Tech

Introduction to Organic Chemistry and Biochemistry

Instructor Dr. Upali Siriwardane (Ph.D. Ohio State)

E-mail: [email protected]

Office: 311 Carson Taylor Hall ; Phone: 318-257-4941;

Office Hours: MWF 8:00 am - 10:00 am;

TT 9:00 – 10:00 am & 1:00-2:00 pm.

December 17, 2010 Test 1 (Chapters 12-13)

January 19, 2011 Test 2 (Chapters 14,15 & 16)

February 7, 2011 Test 3(Chapters 17, 18 & 19)

February 23, 2011 Test 4 (Chapters 20, 21 & 22)

February 24, 2011 Comprehensive Make Up Exam:

Chemistry 121(01) Winter 2010-11


Chapter 15: Aldehyde and Ketones15.1 The Carbonyl Group

15.2 Compounds Containing a Carbonyl Group

15.3 The Aldehyde and Ketone Funcitonal Groups

15.4 Nomenclature for Aldehydes

15.5 Nomenclature for Ketones

15.6 Isomerism for Aldehydes and Ketones

15.7 Selected Common Aldehydes and Ketones

15.8 Physical Properties of Aldehydes and Ketones

15.9 Preparation of Aldehydes and Ketones

15.10 Oxidation and Reduction of Aldehydes and Ketones

15.11 Reaction of Aldehydes and Ketones with Alcohols

15.12 Formaldehyde-Based Polymers

15.13 Sulfur-Containing Carbonyl Groups


Aldehydes: Carbonyl is attached to at least one H atom in aldehydes

Ketones: Carbonyl is directly attached with two carbon atoms in ketones

Carboxylic acids: carbonyl carbon atom bonded to a hydroxyl group.

Esters: carbonyl carbon atom bonded to an oxygen atom

Amide: carbonyl carbon atom bonded to a nitrogen atom

C

O

OH

Carboxylic AcidFunctional Group

C

O

O

EsterFunctional Group

C

O

NH

AmideFunctional Group

Aldehydes and Ketones


Aldehyde functional group: –CHO

Ketone functional group: carbonyl carbon (C=O) attached to carbon atoms

Cyclic aldehydes are not possible but cyclic ketones are known

Cyclic ketones are not heterocyclic ring systems

Aldehyde Functional Group


Structure• the functional group of an aldehyde is a carbonyl group

bonded to a H atom • the functional group of a ketone is a carbonyl group

bonded to two carbon atoms

Propanone(Acetone)

Ethanal(Acetaldehyde)

Methanal(Formaldehyde)

O O O

CH3CHHCH CH3CCH3


Carbonyl group: A carbon atom double-bonded to an oxygen atom

Aldehydes and ketones are the compounds which contain a carbonyl functional group

C=O bond is polar (oxygen gets partial negative and carbon gets partial positive charge) C=C is non polar

All carbonyl groups have a trigonal planar structure

Compounds with C=O and C=C both exhibit different chemistry

C O

CarbonylPolarity of Carbonyl Group

C

O120o120o

120o

Geometry of Carbonyl Group

Carbonyl group:


IUPAC Nomenclature of Aldehyde and Ketones

The IUPAC system deals with functional groups two different ways.

Modification of the hydrocarbon name to indicate the presence of a functional group.

aldehyde, -CHO use -al ending.

Ketones -RCOR’ use -one ending.


IUPAC RulesRule 1: Select as the parent carbon chain the longest carbon

chain that includes the carbon atom of the carbonyl group.

Rule 2: Name the parent chain by changing the “-e” ending of the corresponding alkane name to “-one.”

Rule 3: Number the carbon chain such that the carbonyl carbon atom receives the lowest possible number. The position of the carbonyl carbon atom is noted by placing a number immediately before the name of the parent chain.

Rule 4: Determine the identity and location of any substituents, and append this information to the front of the parent chain name.

Rule 5: Cyclic ketones are named by assigning the number 1 to the carbon atom of the carbonyl group. The ring is then numbered to give the lowest number(s) to the atom(s) bearing substituents.


Example

C - C - C - C - CHO

Base contains 5 carbon

- aldehyde name is pentane

- remove -e and add -al

C - C - C - C - CO-C-C

Base contains 7 carbon

- aldehyde name is heptane

- remove -e and add -one

3-heptanone


Common NamesAldehydes: Fomaldehyde: HCHO

Acetaldehyde: CH3CHO

Propionaldehyde: CH3CH2CHO

Butyraldehyde: CH3CH2CH2CHO

Valeraldehyde: CH3CH2CH2CH2CHO Ketones:

Acetone: CH3COCH3

Methyl ethyl ketone CH3CH2COCH3 Butyl propyl ketone

CH3CH2CH2CH2COCH2CH2CH3


Nomenclature

CHO HO CHO

Cyclopentane-carbaldehyde

trans-4-Hydroxycyclo-hexanecarbaldehyde

14

3-Methylbutanal 2-Propenal(Acrolein)

H

O

(2E)-3,7-Dimethyl-2,6-octadienal(Geranial)

1

2

3

4

5

6

7

8

11

223

3

4H

O

H

O

2-Methyl-cyclohexanone

5-Methyl-3-hexanone

Benzophenone Acetophenone

OO

O O


Nomenclature

HCOOH

O

COOHO

COOHHO

OHHS

COOHNH2

-al oxo-

Ketone -one oxo-

Alcohol -ol hydroxy-

Amino -amine amino-

3-Oxopropanoic acid

3-Oxobutanoic acid

4-Hydroxybutanoic acid

3-Aminobutanoic acid

Example of When the FunctionalGroup Has a Lower Priority

Sulfhydryl -thiol mercapto- 2-Mercaptoethanol

Functional Group Suffix Prefix

Carboxyl -oic acid

Aldehyde


Name the Aldehyde

2,4-dimethylpentanal


Constitutional isomers exist for aldehydes and ketones

Isomers between aldehydes and ketones are called functional group isomers

Two types of isomers:• Skeletal isomers: arrangements of atoms in space

is different.• Positional isomers: Position of the functional group

is different.

O

Butanal

O

2-Methylpropanal

O

2-Pentanone

O

3-Pentanone

Skeletal isomersPositional isomers

Constitutional isomers of aldehydes and ketones


Examples of Aldehyde and KetonesFormaldehyde

Simplest aldehyde and has one carbon atom

It is synthesized by oxidation of methanol

Mainly used for the manufacturing of polymers

Bubbling formaldehyde through water produces formalin (formaldehyde in water with pungent smell)

Formalin is used for preserving biological specimens

In formalin formaldehyde is present in the form of HO-CH2-OH


Examples of Aldehyde and KetonesAcetone is the simplest ketone.

Colorless liquid with mild sweet odor.

Excellent solvent: it is miscible in both water and organic solvents.

Acetone is the main ingredient in gasoline treatments designed to solubilize water in the gas tank and allow it to pass through the engine in miscible form.

Major component of nail polish remover.

Patients with diabetes produce large amounts of acetone.• Diabetic breath has mild sweet odor because of

acetone.• Presence of acetone in urine indicates diabetes.


Important AldehydesMethanal or formaldehyde

Ethanal or acetaldehyde

2-Propanone or acetone

2-Butanone or methyl ethyl ketone

Oil of almonds or benzaldehyde

Oil of Cinnamon or cinnamaldehyde

Oil of vanilla beans or vanillin

Mushroom flavoring or 2-octanone

Oil of lemongrass or citral:


Naturally Occurring Aldehydes and KetonesAldehydes and ketones occur widely in nature

Such compounds have higher molecular masses, pleasant odors and flavors

Often used in consumer products such as perfumes, air fresheners, etc).

Example: Butanedione

The unmistakable odor of melted butter is largely due to the four-carbon diketone - butanedione.


Physical properties of aldehydes and ketones.


Physical State at Room Temperature

Aldehydes:

•C1-C2 aldehydes are gases

•C3-C11 straight-chain aldehydes are liquids

• >C11 aldehydes are solids

Ketones:• Lower molar mass ketones are colorless

liquids


Boiling and Melting Points

Intermediate between alcohols and alkanes

Higher boiling points than alkanes because of dipole–dipole attractions between carbonyl groups in these molecules.

C

O C

O


SolubilityWater molecules can hydrogen-bond with

aldehyde and ketone molecules, which causes low-molecular-mass aldehydes and ketones to be water soluble.

Aldehydes and ketones with longer hydrocarbon chains are less soluble or insoluble in water.


Oxidation of Alcohols

Aldehydes produced by the mild oxidation of primary alcohols

Ketones are produced by the mild oxidation of secondary alcohols

Oxidizing agents(mild): KMnO4 or K2Cr2O7

Preparation of Aldehydes and Ketones


Oxidation of Aldehydes and Ketones:• Aldehydes readily undergo oxidation to

carboxylic acids• Ketones are resistant to oxidation

Reactions of Aldehydes and Ketones


Preapration of Aldehydes:

Partial oxidation of primary alcohols with H2CrO4:


Oxidation of alcohol


Preapration of ketones:

Oxidation of secondary alcohols with KMnO4, or H2CrO4


Oxidation of alcohol


Chemical Reactions

Oxidation of aldehyde.

Benedict's Test for aldehydes:


Test for Urine Glucose: Benedict’s Test


Oxidation of aldehyde.

The commercial manufacture of silver mirrors uses a similar process.

Tollen's Test:


Reduction of als & ones compounds to alcohols:


Addition reactions of als & onesHemiacetal or hemiketal formation


Hemiacetal form of cyclic sugars


Formation of Acetals and Ketals.


Addition of HCN and H2O


Aldol Condensation

In biological systems this reaction is catalysed by an enzyme named aldolase.


Keto & Enol tautomers

keto form enol from


Keto & Enol tautomers in sugars

aldehyde enol ketone


Tollens test: Test for AldehydeTollens test (silver mirror test): Tollens reagent

[aqueous silver nitrate (AgNO3) and ammonia (NH3)] when added to an aldehyde, Ag+ ion is reduced to silver metal, which deposits on the inside of the test tube, forming a silver mirror. • The appearance of this silver mirror is a positive

test for the presence of the aldehyde group.• The Ag ion will not oxidize ketones.

R C

O

H + Ag+NH3, H2O, Heat

R C

O

OH + Ag


Benedict’s Test: Test for Aldehyde

Similar to the Tollens test except that the metal ion oxidizing agent is Cu2+

Cu 2+ ion is reduced to Cu ion, which precipitates from solution as Cu2O (brick-red colored solid)

R C

O

H + Cu2+R C

O

OH + Cu2O


Reduction of Aldehydes and KetonesAldehydes and ketones are easily reduced by

hydrogen gas (H2), in the presence of a catalyst (Ni, Pt, or Cu), to form alcohols. • Aldehydes produces primary alcohols.• Ketones yield secondary alcohols.

R C

O

HNi

R C

O

R

R C

OH

H

H

R C

OH

R

H

+ H2

+ H2Ni

Primary Alcohol

Secondary Alcohol


Aldehydes and ketones react with alcohols to form hemiacetals and acetals.

Hemiacetal formation: A hemiacetal is an organic compound in which a carbon atom is bonded to both a hydroxyl group (—OH) and an alkoxy group (—OR).

A hemiacetal can also be formed due to the reaction between an —OH and C=O functional groups with in the same molecule.

Such a reaction produces a cyclic hemiacetal

Cyclic hemiacetals are more stable

Formation of Hemiacetals and Acetals


Simplest Aldehyde


Practice Exercise

Answers:

a. Yes

b. Yes

c. No

d. Yes


Acetal Formation and Hydrolysis

Acetal Formation: An acetal is an organic compound in which a carbon atom is bonded to two alkoxy groups (—OR).

Acetal Hydrolysis: Undergo hydrolysis in acidic solution to form the aldehyde or ketone and alcohols that originally reacted to form the acetal.


Bakelite


Formaldehyde is a prolific “polymer former”

Under acidic conditions, reaction between formaldehyde and phenol forms a phenol–formaldehyde network polymer


Replacement of carbonyl oxygen with sulfur produces thioaldehydes (thials) and thioketones (thiones)• These are unstable and readily decompose.

Replacement of the carbonyl carbon atom with sulfur produces sulfoxides.• Sulfoxides are much more stable than thiocarbonyls• Most important example: DMSO (dimethyl sulfoxide)• DMSO is an odorless liquid with excellent solvent

properties• DMSO is quickly absorbed into the body and is known

to relieve pain and inflammation• Not approved by the FDA for medical uses because of

possible side effects

Thioaldehydes (thials) and Thioketones

15-1 Chemistry 121, Winter 2011, LA Tech Introduction to Organic Chemistry and Biochemistry...

Documents

Transcript of 15-1 Chemistry 121, Winter 2011, LA Tech Introduction to Organic Chemistry and Biochemistry...