Organic Chem2

7/29/2019 Organic Chem2

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ORGANICCHEMIST

RY

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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Common Functional Groups


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Alcohols: Structure and Physical

Properties

An organic compound containing a hydroxyl group

attached to an alkyl group

Alcohols have the general formula R-OH


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Physical Properties

R-O-H has a structure similar to that of water

Hydroxyl group is very polar

Hydrogen bonds can form readily

12.1

StructureandPhysicalProperties


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Alcohol Boiling Points Alcohols have abnormally high boiling

points relative to their molecular weightsdue to their ability to hydrogen bond

CH3CH2O

H

CH3

CH2

O

H

CH3CH

2OH

Hydrogen bonds

12.1


Hydrogen bonds in Ethane


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Solubility

Low molecular weight alcohols (up to 5-6

carbons) are soluble in water

Very polar

Hydrogen bond with the water molecule CH3CH2OH very soluble

CH3OCH3 barely soluble

CH3CH2CH2CH2OH, 7 g per 100 mL HOCH2CH2CH2CH2OH is very soluble

(two OH groups)

12.1



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High Molecular Weight Alcohol Solubility

As molecular weight increases, alcohols

become insoluble in water

Still polar

Ratio of hydroxyl groups to carbons in the

chain determines solubility

Diols and triols are more soluble than those with

only a single hydroxyl group

12.1



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Medically Important Alcohols

Methanol

Colorless and odorless liquid

Used as a solvent

Toxic, can cause blindness and death if ingested

Can be used as a fuel


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12.3

MedicallyIm

portantAlcohols

An odorless and colorless liquid Widely used as a solvent

The alcohol in alcoholic beverages

Derived from fermentation of

carbohydrates

Beverage produced varies with the starting

material and the fermentation process

Ethanol


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12.3

MedicallyIm

portantAlcohols

Colorless, but has a slight odor

Commonly called rubbing alcohol

Toxic when ingested

Used as a:

Disinfectant Astringent

Industrial solvent

2-Propanol


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12.3

MedicallyIm

portantAlcohols

Used as automobile antifreeze

Has a sweet taste, but is extremely

poisonous

Added to water

Lowers the freezing point Raises the boiling point

1,2-Ethanediol

OH CH2CH2OHethylene glycol(antifreeze)


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12.3

MedicallyIm

portantAlcohols

Very viscous, thick

Has a sweet taste

Non-toxic

Highly water soluble

Used in: Cosmetics

Pharmaceuticals

Lubricants

Obtained as a by-product of fat hydrolysis

1,2,3-Propanetriol

OH CH2CH CH

2OH

OH

glycerol

(in fats,

a moisturizer)


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Phenol Phenols are compounds in which the hydroxyl group is

attached to a benzene ring

Polar compounds due to the hydroxyl group

Simpler phenols are somewhat water soluble

Components of flavorings and fragrances

Phenols have the formula Ar-OH Ar must be an aromatic ring (e.g., Benzene)


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Phenol Derivatives

Widely used in healthcare as:

Germicides

Antiseptics

Disinfectants

12.7

Phenols


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Ethers

Ethers have the formula R-O-R R can be aliphatic or aromatic

Ethers are slightly polar due to the polar C=Obond

Do not hydrogen bond to one another as thereare no OH groups


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Ether Physical Properties

Ethers have much lower boiling points than

alcohols due to the lack of hydrogen bonding

12.8

Ethers


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Medical Uses of Ethers

Ethers are often used as anesthetics

Accumulate in the lipid material of nerve cellsinterfering with nerve impulse transmission

Today halogenated ethers are used routinely as

general anesthetics Less flammable

Safer to store and to work with

CH3 CH2O CH2 CH3Diethyl ether -

First successful

general anesthetic

CH3O C C H

F

F

Cl

Cl

Penthrane12.8Ethers


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Thiols

Thiols have the formula R-SH

Similar in structure to alcohols with S replacing O

Disulfides have the formula R-S-S-R R may be aliphatic or aromatic

Name is based on longest alkane chain with the

suffix thiol position indicated by number

CH2 CH2CH3 CHSH

CH3

3-methy-1-butanethiol


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Thiols and Scent

Thiols, as many other sulfur-containing

compounds can have nauseating aromas Defensive spray of North American striped skunk

Onions and garlic

Compare with pleasant scents below

12.9

Thiols


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Carbonyl Compounds

Contain the carbonyl groupC=O

Aldehydes:R may be hydrogen,

usually a carbon

containing group

Ketones:

R contains carbon

R CO

H RCHO

R C

O

R RCOR

Short

forms


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Structure and Physical Properties

Aldehydes and ketones are polar compounds

The carbonyl group is polar

The oxygen end is electronegative

Can hydrogen bond to water Cannot form intermolecular hydrogen bond

C

O

+-

C

O H O

H

Hydrogenbond

1


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Hydrogen Bonding in Carbonyls

13

.1StructureandPhysicalPropertie

s

Bonding with H2O Intermolecular


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Physical Properties

Carbonyls boil at

Higher temperatures than:

Hydrocarbons

Ethers

Lower temperatures than:

Alcohols


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Important Aldehydes and Ketones

Methanal (b.p. 21

oC) is a gas used in aqueous

solutions as formalin to preserve tissue

Ethanal is produced from ethanol in the livercausing hangover symptoms

Propanone (Acetone) is the simplest possibleketone

Miscible with water

Flammable

Both acetone methyl ethyl ketone (MEK or butanone)are very versatile solvents


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Important Uses of Carbonyl Compounds

Used in many industries

Food chemicals

Natural food additives

Artificial additives Fragrance chemicals

Medicines

Agricultural chemicals

CH3

CH2

C

O

CH35

OH CO

H

CH3O

VanillinVanilla beans

2-octanone

Mushroom flavor13.3

ImportantAldehydesandKeton

e


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Other Important Carbonyls

13

.3ImportantAldehydesandKeton

e


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Other Important Carbonyls

13

.3ImportantAldehydesandKeton

e


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Carboxylic Acid and Esters


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Carboxylic Acids

Structure

Carboxylic acid groups consist of twovery polar functional groups

Carbonyl group

Hydroxyl group Carboxylic acid groups are very polar

Carboxylic acid Ester

propanoic acid methyl ethanoate


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Physical Properties

Low molecular weight carboxylic acids Sharp, sour taste

Unpleasant aromas

High molecular weight carboxylic acids

Fatty acids important in biochemistry

Low molecular weight carboxylic acids are watersoluble due to hydrogen bonding with:

Water

Each other

14

.1CarboxylicAcids


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Physical Properties

Due to carboxylic acids forming intermolecularhydrogen bonds boiling points are at higher

temperatures than those of any other functional

group studied

14

.1CarboxylicAcids


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Some Important Carboxylic Acids

CH3CH

2C

O

OH16

Stearic acidfound in beef fat

14

.1CarboxylicAcids


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Esters

Structure and physical properties

Esters are mildly polar, somewhat water soluble Frequently found in natural foodstuffs

Many have pleasant aromas Isoamyl acetate = banana oil

3-methylbutyl ethanoate Ethyl butanoate = pineapple aroma

Ethyl butanoate

Isobutyl formate = raspberry aroma

Isobutyl methanoate

Boil at approximately the same temperature ascarbonyls with comparable molecular weight


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Saponification

Saponification (soap-making) is:

Base-catalyzed hydrolysis of fats (glycerol triesters)


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Simplified Action of Soap

14.2

Esters


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Amines

Amines are derivatives of ammonia

Most important type of organic base found in

nature

Consider as if substituted ammonia: RNH2

R2NH

R3N R can be either aliphatic or aromatic


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Comparison of NH3 to Amines

15

.1Amines


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Physical Properties

Amines form hydrogen bonds but not as stronglyas alcohols Nitrogen is less electronegative than oxygen

Tertiary amines cannot hydrogen bond to eachother

15

.1Amines


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Boiling Points

Amines have boiling points between alkanes and

alcohols

Tertiary amines boil lower then 1o or 2o of similar

molecular weight

15

.1Amines


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Solubility

All amines can form

hydrogen bonds withwater

Amines up to 6carbons long are

water soluble due tothis hydrogenbonding

Water solubilitydecreases as thelength of thehydrocarbon portionof the moleculeincreases

CH3N

H

HH

O

H

HO

H

15.1

Amines


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Medically Important Amines

Amphetamines

stimulate the

central nervoussystem

Analgesics (pain

relievers) and

anesthetics (painblockers)

15.1

Amines


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Medically Important Amines

Decongestants

shrink the

membranes lining

the nasal passages

Sulfa drugs (first

chemicals used tofight infections) are

also made from

amines

15.1

Amines


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Amides

Amides are formed in a reaction between acarboxylic acid derivative and an amine orammonia

The amide bond is the bond formed between:

Carbonyl group from the carboxylic acid

Amino group from the amine or ammonia


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Physical Properties

Most amides are solids at room temperature due tointernal hydrogen bonding

They are not bases

A resonance structure shows why the N lone pair is

unavailable to accept a proton

15.1

Amines


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Amide Hydrogen Bonding

Strong intermolecularhydrogen bondingbetween the N-H bondof one amide and the

C=O bond of another Very high boiling

points

Simple amides are

quite soluble in water

15.1

Amines


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Preview of Amino Acids, Proteins, and

Protein Synthesis

A protein is a polymer of amino acids linked by theamide bonds

As the amino group and the carboxyl group link,

water is lost

Organic Chem2

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