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ORGANIC CHEMISTRY III

• CARBOXYLIC ACIDS• DERIVATIVES OF ACIDS• ALDEHYDES/KETONES• AMINES• ETHERS• Chapter 15.4 Silberberg

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Chapter 15

Organic Compounds and the

Atomic Properties of Carbon

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Organic Compounds and the Atomic Properties of Carbon

15.3 Some Important Classes of Organic Reactions

15.4 Properties and Reactivities of Common Functional Groups

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Goals & Objectives

• See the following Learning Objectives on page 676.

• Master these Skills:• 15.6, 8-10.

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Table 15.5 Important Functional Groups in Organic Compounds

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Table 15.5 Important Functional Groups in Organic Compounds

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Amines

The amine functional group contains a N atom.

The systematic name for an amine is formed by dropping the final –e of the alkane and adding the suffix –amine.

C N

Common names that use the name of the alkyl group followed by the suffix –amine are also widely used.

CH3CH2NH2

ethanamine ORethylamine

CH3CH2 NH CH2CH3

diethylamine

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Figure 15.17 General structures of amines.

Amines are classified according to the number of R groups directly attached to the N atom.

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Figure 15.18 Some biomolecules with the amine functional group.

Lysine (1° amine)amino acid found in proteins

Adenine (1° amine)component of nucleic acids

Epinephrine (adrenaline; 2° amine)neurotransmitter in brain; hormone released during stress

Cocaine (3° amine)brain stimulant; widely abused drug

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Properties and Reactions of Amines

Primary and secondary amines can form H bonds; therefore they have higher melting and boiling points than hydrocarbons or alkyl halides of similar mass.

Amines of low molar mass are fishy smelling, water soluble, and weakly basic.

Tertiary amines cannot form H bonds between their molecules because they lack a polar N–H bond.

Amines undergo a variety of reactions, including substitution reactions.

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Sample Problem 15.4 Predicting the Reactions of Alcohols, Alkyl Halides, and Amines

PLAN: We first determine the functional group(s) of the reactant(s) and then examine any inorganic reagent(s) to decide on the reaction type. Keep in mind that, in general, these functional groups undergo substitution or elimination.

PROBLEM: Determine the reaction type and predict the product(s) for each reaction:

(a) CH3 CH2 CH2 I + NaOH

(b) CH3 CH2 CH2 Br + 2 CH3 CH2 CH2 NH2

(c) CH3 CH

OH

CH3

Cr2O72-

H2SO4

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SOLUTION:

Sample Problem 15.4

(a) In this reaction the OH of the NaOH reaction substitutes for the I in the organic reagent:

CH3 CH2 CH2 OH + NaI

(b) This is a substitution reaction:

CH3 CH2 CH2 NH

CH2CH3

+ CH3 CH2 CH2 NH2Br

(c) This is an elimination reaction since acidic Cr2O72- is a strong

oxidizing agent:CH3 C

O

CH3

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Amines

• Classification• NH3 RNH2 R2NH R3N

• 1O 2O 3O

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Amines

• Nomenclature• CH3NH2

• (CH3)2NH

• (CH3)3N

• CH3NHCH2CH3

• (CH3)2NCH2CH3

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Amines

• Reactions– organic bases– RNH2 + H2O ---> RNH3

+ + OH-

– CH3NH2 + HCl ---> CH3NH3+ + Cl-

– CH3NH2.

HCl– methylamine

hydrochloride

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Aldehydes and Ketones

Aldehydes and ketones both contain the carbonyl group, C=O.

Aldehydes are named by replacing the final –e of the alkane name with the suffix –al.

Ketones have the suffix –one and the position of the carbonyl must always be indicated.

R and R′ indicate hydrocarbon groups.

H C

O

Raldehyde

R C

O

R'ketone

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Figure 15.20 Some common aldehydes and ketones.

Methanal (formaldehyde) Used to make resins in plywood, dishware, countertops; biological preservative

Ethanal (acetaldehyde) Narcotic product of ethanol metabolism; used to make perfumes, flavors, plastics, other chemicals

2-Propanone (acetone) Solvent for fat, rubber, plastic, varnish, lacquer; chemical feedstock

2-Butanone (methyl ethyl ketone) Important solvent

Benzaldehyde Artificial almond flavoring

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Figure 15.21 The polar carbonyl group.

The C=O bond is electron rich and is also highly polar. It readily undergoes addition reactions, and the electron-poor C atom attracts electron-rich groups.

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Reactions of Aldehydes and Ketones

Reduction to alcohols is an example of an addition reaction:

O

reduction

OH

cyclobutanone cyclobutanol

Organometallic compounds, which have a metal atom covalently bonded to C, add to the electron-poor carbonyl C:

R C

O

H + R' Li+-

+

-

R CH

OH

R' + LiOH

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Sample Problem 15.5 Predicting the Steps in a Reaction Sequence

PLAN: For each step we examine the functional group of the reactant and the reagent above the yield arrow to decide on the most likely product.

PROBLEM: Fill in the blanks in the following reaction sequence:

CH3 CH2 CH

Br

CH3OH- Cr2O7

2-

H2SO4

CH3-Li H2O

SOLUTION: The first step involves an alkyl halide reacting with OH-, so this is probably a substitution reaction, which yields an alcohol. In the next step the alcohol is oxidized to a ketone and finally the organometallic reagent adds to the ketone to give an alcohol with one more C in its skeleton:

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Sample Problem 15.5

CH3 CH2 CH

Br

CH3OH- Cr2O7

2-

H2SO4

CH3-Li

H2O

CH3 CH2 CH

OH

CH3

substitution oxidation(elimination)

CH3 CH2 C

O

CH3

addition

CH3 CH2 C

OH

CH3

CH3

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Aldehydes

• Nomenclature• IUPAC

TRIVIAL• HCHO• CH3CHO

• CH3CH2CHO

• CH3CH2CH2CHO

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O

methanalO

ethanal

O

propanal

O

butanal

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Aldehydes

• Preparation– RCH2OH + [O] ---> RCHO

– CH3CH2OH + [O] ---> CH3CHO

– Prepare• 3-methylpentanal• 2,4-dimethylhexanal

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Ketones, RCOR’

• Nomenclature• IUPAC

TRIVIAL• CH3COCH3

• CH3COCH2CH3

• CH3COCH2CH2CH3

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O

propanone

O

2-butanone

O

2-pentanone

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Ketones

• Preparation– OH– RCHR’ + [O] ---> RCOR’– OH– CH3CHCH3 + [O] ---> CH3COCH3

• Prepare:– 3-hexanone– 2-methyl-3-pentanone

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Carboxylic Acids

Carboxylic acids are named by replacing the –e of the alkane with the suffix –oic acid.

Carboxylic acids contain the functional group –COOH, or

Carboxylic acids are weak acids in water, and react with strong bases:

C

O

OH

CH3 C

O

OH (l) + NaOH (aq) CH3 C

O

O- (aq) + Na+ (aq) + H2O (l)

methanoic acid methanoate anion

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Figure 15.22 Some molecules with the carboxylic acid functional group.

Methanoic acid (formic acid) An irritating component of ant and bee stings

Butanoic acid (butyric acid) Odor of rancid butter; suspected component of monkey sex attractant

Octadecanoic acid (stearic acid) Found in animal fats; used in making candles and soaps

Benzoic acid Calorimetric standard; used in preserving food, dyeing fabric, curing tobacco

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Carboxylic Acids, RCOOH

• Nomenclature• IUPAC TRIVIAL• HCOOH• CH3COOH

• CH3CH2COOH

• CH3CH2CH2COOH

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OHO

methanoic acid

O

OH

ethanoic acid

O

OH

propanoic acid

O

OH

butanoic acid

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Carboxylic Acids, RCOOH

• Preparation– RCH2OH + xs[O] ----> RCOOH

– CH3CH2OH + xs[O] ----> CH3COOH

• Reaction--as acid– RCOOH + NaOH ----> RCOONa– CH3COOH + NaOH ----> CH3COONa

– sodium acetate

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Derivatives of Carboxylic Acids

• Acid Chlorides, RCOCl– Nomenclature

• “oic acid” becomes ‘yl chloride”• CH3CH2COCl

– Preparatio• RCOOH + PCl3 ----> RCOCl

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Esters

The ester group is formed by the reaction of an alcohol and a carboxylic acid.

Ester groups occur commonly in lipids, which are formed by the esterification of fatty acids.

CH3 C

O

OH O CH3H+ CH3 C

O

O CH3 + HOH

ethanoic acid methanol methyl ethanoate

Esterification is a dehydration-condensation reaction.

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Figure 15.23 Some lipid molecules with the ester functional group.

Cetyl palmitate The most common lipid in whale blubber

Lecithin Phospholipid found in all cell membranes

Tristearin Typical dietary fat used as an energy store in animals

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Derivatives of Carboxylic Acids

• Esters, RCOOR’– Preparation and Nomenclature– RCOCl + R’OH ----> RCOOR’ + HCl– CH3COCl + CH3CH2OHCH3COOCH2CH3

– ethyl acetate

– or ethyl ethanoate

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Table 1. Names, Structures, and Fruit and Flower Aromas of Some Common Natural EstersEster Name Aroma

3-Methylbutyl acetate Bananas n-Butyl acetate Pears

n-Octyl acetate Oranges

Benzyl acetate Peaches

Benzyl butyrate Flowers*

Ethyl butyrate Pineapples

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O

O

3-Methylbutyl acetate

O

O

n-Butyl acetate

O

O

n-Octyl acetate

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O

O

Benzyl acetate

O

O

Benzyl butyrate

O

O

Ethyl butyrate

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Saponification

Ester hydrolysis can be carried out using either aqueous acid or aqueous base. When base is used the process is called saponification.This is the process used to make soaps from lipids.

R C

O

O CH2

CH

CH2O

O

C

O

R"

C

O

R'

a triglyceride

3NaOH

HO CH2

CH

CH2HO

HO

R C

O

O- Na+

R' C

O

O- Na+

R" C

O

O- Na+

3 soaps(salts of fatty acids)

glycerol

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Amides

An amide contains the functional group:

C

O

N

Amides, like esters, can be hydrolyzed to give a carboxylic acid and an amine.

The peptide bond, which links amino acids in a protein, is an amide group.

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Lysergic acid diethylamide (LSD-25)A potent hallucinogen

Figure 15.24 Some molecules with the amide functional group.

N,N-Dimethylmethanamide (dimethylformamide)Major organic solvent; used in production of synthetic fibers

AcetaminophenActive ingredient in nonaspirin pain relievers; used to make dyes and photographic chemicals

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Derivatives of Carboxylic Acids

• Amides, RCONH2

– Preparation and Nomenclature– RCOCl + NH3 ----> RCONH2 + HCl

– CH3COCl + NH3 ----> CH3CONH2

– ethanamide– acetamide

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Sample Problem 15.6 Predicting the Reactions of the Carboxylic Acid Family

PROBLEM: Predict the product(s) of the following reactions:

(a) CH3 CH2 CH2 C

O

OH CH3 CH

OH

CH3+H+

(b) CH CH2 CH2 C

O

NH

CH3

CH3 CH2CH3

NaOH

H2O

PLAN: We identify the functional groups in the reactant(s) and see how they change. In (a), a carboxylic acid reacts with an alcohol, so the reaction must be a substitution to form an ester. In (b), an amide reacts with aqueous base, so hydrolysis occurs.

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Sample Problem 15.6

SOLUTION:

(a) CH3 CH2 CH2 C

O

OH CH3 CH

OH

CH3+H+

CH3 CH2 CH2 C

O

O CH

CH3

CH3

+ H2O

(b) CH CH2 CH2 C

O

NH

CH3

CH3 CH2CH3

NaOH

H2OCH CH2 CH2 C

OCH3

CH3 O- Na+

CH2CH3

+NH2

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Ethers, ROR’

• HOH ROH ROR’• water alcohol ether

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Ethers, ROR’

• Nomenclature• Use common names• CH3OCH3

• CH3OCH2CH3

• CH3OCH2CH2CH2CH3

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O

methoxymethane

O

methoxyethane

O

methoxybutane

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Alexander Williamson

• Alexander William Williamson (May 1, 1824 – May 6, 1904), an English chemist, was born at Wandsworth, London. Williamson is remembered for his research on the formation of ether. For his work on etherification, Williamson received a Royal medal from the Royal Society in 1862.

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Ethers, ROR’

• Preparation (Williamson synthesis)• RONa + R’I ---> ROR’ + NaI• Outline a synthesis of each of the

following:• ethylmethyl ether• ethoxybutane

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Polymers

Addition polymers, also called chain-growth polymers form when monomers undergo an addition reaction with each other.The monomers of most addition polymers contain an alkene group.

Condensation polymers are formed when monomers link by a dehydration-condensation type reaction.The monomers of condensation polymers have two functional groups, and each monomer can link to two others.

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Figure 15.27 Steps in the free-radical polymerization of ethylene.

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Table 15.6 Some Major Addition Polymers

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Table 15.6 Some Major Addition Polymers

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Figure 15.28 The formation of nylon-66.

Nylon-66 is a condensation polymer, made by reacting a diacid with a diamine. The polyamide forms between the two liquid phases.

HO C

O

(CH2)4 C

O

OH + nH2N (CH2)6 NH2

HO C

O

(CH2)4 C

O

NH (CH2)6 NH Hn