organic chemistry and hydrocarbons - by razi

7/29/2019 Organic Chemistry and Hydrocarbons - By Razi

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Chapter 14

Organic Chemistry

ANDHYDROCARBONS


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Organic Chemistry -Introduction Organic chemistry is the study of carbon

compounds.

Animals, plants, and other forms of lifeconsist of organic compounds.

Nucleic acids, proteins, fats, carbohydrates,enzymes, vitamins, and hormones are all

organic compounds.

Biochemistry was developed later as thestudy of the chemical compounds and

reactions in living cells.Intro


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Organic Chemistry -Introduction Scientists had originally thought that organic

compounds contained a vital force due to

their natural origin. This was disproved by Friedrich Whler in 1828.

Whler was able to make urea, a carbon

compound in human urine, in the laboratory

from a mineral. Organic chemistry is an enormous field.

In this chapter we will investigate some of the

fundamental concepts.Intro


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Bonding in OrganicCompounds Besides carbon, the most common elements

in organic compounds are hydrogen, oxygen,

nitrogen, sulfur, and the halogens.

All of the preceding elements are non-metals,

therefore organic compounds have covalent

bonding.

Any structural formula that obeys the bonding

rules in the following table probablyrepresents a possible compound.

A drawn structure that breaks the bonding rules is

unlikely to exist.

Section 14.1


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Common Elements inOrganic CompoundsApplication of the octet ruleindicates that these elementsshould bond as shown below:

Section 14.1


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Identifying Valid & IncorrectStructural FormulasAn Example

Two structural formulas are shown above.Which on does not represent a real compound?

In structure (a) each H and halogen has onebond, each C has four bonds, and each O hastwo bonds.

This is a valid structure.

Section 14.1


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Identifying Valid & IncorrectStructural FormulasAn Example

As we examine (b), we note that each H hasone bond, each C has four bonds, the N has

three bonds, BUT the O has three bonds. The O should only have two bonds.

Therefore (b) is not a valid structure.

Section 14.1


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Structural FormulasConfidence Exercise

The structural formula above appears in a

recent chemistry book. Check the number ofbonds to each atom and determine whether

any bonding rules are violated.

Section 14.1


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Identifying IncorrectStructural FormulasConfidence Exercise

This is not a valid

structure for caffeine!

O should havetwo bonds, C

should have 4

bonds

Each N should

have 3 bonds

Each Cshould have 4

bonds

Section 14.1


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Hydrocarbons Hydrocarbons are the most simple organic

compounds.

Hydrocarbons contain only carbon (C) andhydrogen. (H)

For classification purposes, all other organiccompounds are considered derivatives of

hydrocarbons. Hydrocarbons can be divided into aromatic and

aliphatic hydrocarbons.

Section 14.2


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Classification ofHydrocarbons

Section 14.2


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Aromatic Hydrocarbons Aromatic hydrocarbons contain one or

more benzene ring.

Benzene (C6H6) is the most importantaromatic hydrocarbon.

It is a clear, colorless liquid with a

distinct odor, and is a carcinogen(cancer-causing agent.)

Traditional Lewis Structure

Section 14.2


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BenzeneStructural Formulas andShort-hand Symbols The Lewis structure and the Kekul symbol both

indicate that the carbons in the ring have alternating

double and single bonds.

Section 14.2


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Other AromaticHydrocarbons Toluene is used in modeling glue. Naphthalene is use

in mothballs, and Phenanthrene are used in the

synthesis of dyes, explosives, and drugs.

Section 14.2


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Benzene representation Benzene representation

howing a flat molecule withsix delocalized electronsforming an cloud above

and below the plane of thering.

Properties of the benzenemolecule and advancedbonding theory indicate

this structure. Thesix electrons appear to beshared by all the carbonatoms in the ring.

Section 14.2


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Substituted for the Hs in theBenzene RingA vast array of other compoundscan be produced

Section 14.2


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Drawing Structures forBenzene DerivativesAn Example Draw the structural formula for 1,3-

dibromobenzene.

First, Draw a benzene ring.

Section 14.2


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raw ng ruc ures orBenzene DerivativesAn Example (cont.)

Second, attach a bromine atom (bromo)

to the carbon atom at the ring position

you choose to be number 1.

Section 14.2


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Drawing Structures forBenzene DerivativesAn Example (cont.)

Third, attach a second (di) bromine atom to

ring position 3 (you may number either

clockwise or counterclockwise from carbon 1)and you have the answer.

1,3-dibromobenzene

Section 14.2


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Structures for BenzeneDerivativesConfidence Exercise Which of the models below most

accurately represents the hydrogen

cyanide molecule, HCN?

From Ebbing/Gammon 7th Ed., p. 380

Section 14.2


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DerivativesConfidence Exercise(cont.) C in (b) only has three bonds. C in (c) only has two bonds & N only has one.

C in (d) only has three bonds & N only hastwo.

Therefore, (a) appears to be the mostaccurate representation of the hydrogencyanide molecule, HCN.

N has three bonds, C has four bonds, H has one

From Ebbing/Gammon 7th

Ed., p. 380

Section 14.2


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Drawing Structures forBenzene DerivativesConfidence Exercise Draw the structural formula for 1-chloro-2-

fluorobenzene.

1. Draw a benzene ring.

3. Attach a fluorine atom to

ring position 2 and you

have the answer.

1-chloro-2-fluorobenzene

Section 14.2

Cl

F

2. Attach a chlorine atom (chloro) to the carbon atom at

the ring position you choose to be number 1.


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Aliphatic Hydrocarbons Aliphatic hydrocarbons are hydrocarbons

having no benzene rings.

Aliphatic hydrocarbons can be dividedinto four major divisions:

Alkanes

Cycloalkanes

Alkenes

Alkynes

Section 14.3


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Classification ofHydrocarbons

Section 14.3


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Alkanes Alkanes are hydrocarbons that contain only

single bonds.

Alkanes are said to be saturated hydrocarbons Because their hydrogen content is at a maximum.

Alkane general formula CnH2n + 2 The names of alkanes all end in -ane.

Methane butane are gases Pentane C17H36 are liquids

C18H38 and higher are solids

Section 14.3


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theAlkane SeriesAll satisfy the general formulaCnH2n+ 2

Section 14.3


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Visualization of anAlkanes Structure

Section 14.3

Structural formula a graphicalrepresentation of the way atomsare connected

Condensed structural formula

save time/space and areconvenient

Ball-and-Stick models 3D

models that can be built bystudents


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Models of Three Alkanes

Names, Structural Formulas, Condensed StructuralFormulas, and Ball-and-Stick Models

Section 14.3


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Methane TetrahedralGeometryBall-and-

Stick &

Space-

FillingModels

Carbons

four single

bonds form

angles of

109.5o

Section 14.3


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Alkanes Energy RelatedProducts Methane = primary component of natural

gas

Propane & Butane = primary componentof bottled gas

Gasoline = pentane to decane

Kerosene = alkanes with n = 10 to 16 Alkanes with n > 16 diesel fuel, fuel

oil, petroleum jelly, paraffin wax,lubricating oil, and asphalt

Section 14.3


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Alkane Products Alkanes are also found in paints, plastics,

drugs, detergents, insecticides, and cosmetics.

Only 6% of the petroleum consumed goes into

making these products. The remaining 94% of the petroleum is burned

as one of the various energy-related products.

Although alkanes are highly combustible, they

are otherwise not very reactive.

Any reaction would require the breaking of the

strong CH and CC bonds.

Section 14.3


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Alkyl Group Alkyl group contains one less hydrogen

than the corresponding alkane.

In naming this group the -ane isdropped and -yl is added.

For example, methane becomes methyl.

Ethane becomes ethyl.

Section 14.3


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This group does not existindependently but occurs bondedto another atom or molecule.

Section 14.3


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Constitutional Isomers Compounds that have the same molecular

formula but different structural formulas

In the case of many alkanes there is more thanone way to arrange the atoms

For example butane and isobutane

Both of these alkanes have the molecular

formula of C4H10

But their structural formula and arrangement is

quite different

Section 14.3


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ButaneContinuous-Chain or Straight-Chain StructureC4H10B

a

l

l

-a

n

d

-S

t

i

c

kSection 14.3


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Isobutane (2-methylpropane)Branched-chain Structure

C4H10B

a

l

l

-a

n

d

-S

t

i

c

k Section 14.3


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Constitutional Isomers Constitutional Isomers may exist

whenever it is possible to construct a

different structural arrangement: Using the same number and types of atoms

Without violating the octet rule

In other words, the same atoms may beconnected to one another in different, but

valid, ways.

Section 14.3


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Number of PossibleIsomers of Alkanes Carbon Atoms

can bond in

many different

ways

Section 14.3


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Organic CompoundNomenclature Due to the large number, variety, and

complexity of organic compounds, a

consistent method of nomenclature hasbeen developed.

Section 14.3


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ys em oNomenclatureFor Alkanes Compound is named as a derivative of the

longest continuous chain of C atoms.

Positions & names of the substituents added

If necessary, substituents named alphabetically More than one of same type substituent di, tri, tetra

The C atoms on the main chain are numbered

by counting from the end of the chain nearest

the substituents.

Each substituent must have a number.

Section 14.3


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An Example to Consider The longest continuous chain of C atoms is five

Therefore this compound is a pentane

derivative with an attached methyl group

Start numbering from end nearest the substituent The methyl group is in the #2 position

The compounds name is 2-methylpentane.

Section 14.3


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Substituents in OrganicCompounds

Section 14.3


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w u uNameAn Example

Draw the structural formula for2,3-dimethylhexane.

Note that the end name is hexane .

Draw a continuous chain of six carbon(C) atoms, with four bonds around each.

Section 14.3


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raw ng a ruc ure rom aNameAn Example (cont.)

Number the C atoms from right to left.

Attach a methyl group (CH3--) to carbon

number 2 and number 3.

Add necessary H atoms.

2,3-dimethylhexane

Section 14.3


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raw ng a ruc ure rom aNameConfidence Exercise

Draw the structural formula for

2,2,4-trimethylpentane.

Note that the end name ispentane .

Draw a continuous chain of five carbon

(C) atoms, with four bonds around each.

Section 14.3


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a NameConfidence Exercise(cont.)

Number the C atoms from right to left.

Attach two methyl groups (CH3--) to carbon

number 2 and one to number 4.

Section 14.3


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Drawing a Structure from aNameConfidence Exercise (cont.)

Add necessary H atoms. 2,2,4-trimethylpentane

Section 14.3


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2,2,4-trimethylpentaneBall-and-Stick Model

Copyright Bobby H. Bammel. All rights reserved.

Section 14.3


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Cycloalkanes Members of the cycloalkane group

possess rings of carbon atoms.

They have the general formula CnH2n.

Each carbon atom is bonded to a total of

four carbon or hydrogen atoms.

The smallest possible ring consists of

cyclopropane, C3H6.

Section 14.3


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The First FourCycloalkanes

Note that in the condensed structural formulas, there is a

carbon atom at each corner and enough hydrogens are

assumed to be attached to give a total of four single bonds.

Section 14.3


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Drawing the Structure of aCycloalkane Draw the geometric figure indicated by

the compounds name , pentane.

Section 14.3


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Drawing the Structure of aCycloalkane Place each substituent on the ring in the

numbered position 1 chloro-2-ethyl-

1-chloro-2-ethylcyclopentane

Section 14.3


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Alkenes Members of the alkene group have a double

bond between two carbon atoms.

One hydrogen atom has been removed fromtwo adjacent carbon atoms, thereby allowingthe two adjacent carbon atoms to form adouble bond.

General formula is CnH2n Begins with ethene (ethylene)

C2H4

Section 14.3


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Some Members of theAlkene Series

Section 14.3


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Naming Alkenes -anesuffix for the corresponding alkane is

changed to -enefor alkenes.

A number preceding the name indicates the C

atom on which the double bond starts. The carbons are numbered such that the double

bond has the lowest number.

For example, 1-butene and 2-butene

Section 14.3


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Alkenes are very Reactiveand are termedunsaturatedhydrocarbons Alkenes will characteristically react with hydrogen to

form the corresponding alkane.

Section 14.3


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Alkynes Members of the alkyne group have a triple

bond between two carbon atoms.

Two hydrogen atoms have been removed

from each of two adjacent carbon atoms,

thereby allowing the two adjacent carbonatoms to form a triple bond.

General formula is CnH2n-2

Begins with ethyne (acetylene) C2H2

Section 14.3


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Some Members of theAlkyne Series

Section 14.3


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Alkynes are UnsaturatedHydrocarbons Due to the triple carbon bond, each alkyne molecule

can react with two molecules of hydrogen.

Section 14.3


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Derivatives ofHydrocarbons Organic molecule characteristics depend on

the number, arrangement, and type of atoms.

Functional Group any atom, group of atoms,or organization of bonds that determine

specific properties of a molecule

Generally the functional group is the reactive part of

the molecule. Due to the functional groups presence, certain

predictable properties ensue.

Section 14.4


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Derivatives ofHydrocarbons Examples of functional groups include:

The double bond in alkenes & triple bond in

alkynes.

Cl atom, F atom,OH group, methyl (CH3)

group.

Derivatives of hydrocarbons are organic

compounds that contain atoms other thanC and H.

Section 14.4


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Alkyl Halides Alkyl halides have the general formula RX,

where X is a halogen and R is an alkyl group

CFCs (chlorofluorocarbons) are examples of

alkyl halides.

A well known CFC is dichlorodifluoromethane

(Freon-12)

Extensively used in the past in cooling devices.

Section 14.4


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Alkyl Halides Another example of an alkyl halide is

chloroform. In the past it was used as a surgical anesthetic but

it is now a known carcenogen.

Carbon tetrachloride was also usedextensively in the past, until it was linked toliver damage.

Section 14.4 w u


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IsomersAn Example

Draw the structural formulas for the two alkylhalide isomers that have the molecular formulaC

2

H4

Cl2

.

Recall that C atoms form four bonds, H & Clform one bond each.

Draw a two-carbon backbone.

Add enough bonds so that each C has four.

Section 14.4 Drawing Constitutional


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IsomersAn Example (cont.) Note, there are just enough open bonds to attach thefour H and two Cl atoms. Fill in the Cl atoms in as many ways as possible.

Remember that you are constrained by the tetrahedralgeometry (109.5o) of the four C bonds.

Fill in the open bonds

with H atoms and name

the compounds.

Section 14.4 raw ng ons u ona


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IsomersConfidence Exercise

Two constitutional isomers of C3H7F exist.Draw the structure for each.

Note that the formula ratio is that of an alkane.

Draw a three-carbon backbone. Add enough bonds so that each C has four.

Section 14.4 w u


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IsomersConfidence Exercise (cont.)

Note, there are just enough open bonds toattach the seven H and the one F atoms.

Fill in the F atoms in as many ways as

possible.

Remember that you are constrained by thetetrahedral geometry (109.5o) of the four Cbonds.

Section 14.4 raw ng ons u ona


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IsomersConfidence Exercise (cont.)

Fill in the open bonds with H atoms andname the compounds.

1-Fluoropropane 2-Fluoropropane

Section 14.4


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Alcohols

Alcohols are organic compounds containingthe hydroxyl group, OH, attached to an

alkyl group.

General formula is ROH

Their IUPAC (International Union of Pure andApplied Chemistry) names end in -ol.

The most simple alcohol is methanol

Also called methyl alcohol or wood alcohol.

(poisonous)

Section 14.4


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Alcohols

Another common alcohol is ethanol.(CH3CH2OH)

Also known as ethyl alcohol or grain alcohol

Least toxic and most important of the alcohols

Ethanol is used in alcoholic beverages,perfumes, dyes, and varnishes.

Section 14.4


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Other Alcohol Examples Rubbing alcohol is

another alcohol

example.

Also known as 2-

hydroxypropane or

isopropyl alcohol

Ethylene glycol is an

alcohol used widely asan antifreeze and

coolant.

Section 14.4


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Carbohydrates Compounds that contain multiple

hydroxyl groups in their molecularstructure.

Names end in -ose

Sugars, starches, and cellulose are themost important carbohydrates.

Glucose (C6H12O6) and fructose(C6H12O6) are important sugars.

Note that glucose and fructose are isomers.

Section 14.4 Structures of Glucose,


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Fructose,and Sucrose Glucose &

Fructose bond

together to formSucrose + H2O

Section 14.4


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Carbohydrates - Sugars Fructose is the sweetest of all sugars and

is found in fruits and honey.

Glucose (also called dextrose) is found insweet fruits, such as grapes and figs, in

flowers, and in honey.

Carbohydrates must be broken down intoglucose for circulation in the blood.

Section 14.4


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Carbohydrates - Starch Starch consists of very long chains (up to

3000 units) of glucose.

Produced by plants in their seeds, tubers,and fruits

When these plants parts are eaten, our

digestive processes covert the starchesback into glucose.

Section 14.4


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Carbohydrates - Cellulose Cellulose is also a polymer of glucose and has

the general formula (C6H10O5)n. Slightly different structure with different properties

than starches Cell walls of plants are dominantly composed

of cellulose.

Humans do not have the appropriate enzymes

(called cellulases) to break cellulose down. Termites and many herbivores contain bacteria

that allow the breakdown of cellulose.

Section 14.4


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Amines Organic compounds that contain nitrogen and

are basic (alkaline) are called amines.

General formula for an amine is RNH2.

One or two additional alkyl groups could be

attached to the N atom, in place of H atoms. Amine examples include methylamine,

dimethylamine, and trimethylamine.

Section 14.4


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Amines Strong Odors

Most simple amines have strong odors. The odor given off by raw fish is due to an

amine that it contains.

Two particularly foul smelling amines are

formed by decaying flesh.

Cadaverine (1,5-diaminopentane)

Putresine (1,4-diaminobutane)

Section 14.4


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Amines - Medicinal

Many amines have medicinal applications. Amphetamines raise the glucose level in the

blood resulting in less fatigue and hunger.

These synthetic drugs certainly have legitimate

medical uses, but can be addictive and lead toinsomnia, excessive weight loss, and paranoia.

Benzedrine is one type of amphetamine.

Section 14.4 The French artist David


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portrays The Death ofSocrates due to the deadlyalkaloid coniine

Section 14.4


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Carboxylic Acids Carboxylic acids contain the carboxyl

group . (COOH)

They have the general formula RCOOH.

Section 14.4


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Carboxylic Acids Formic acid is the simplest

carboxylic acid.

This is the substance that

causes the painful sting ofinsect bites.

Vinegar is a 5% solution of

acetic acid.

Section 14.4


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Esters Ester a compound that has

the following general formulaRCOOR

In the general formula for an ester the R andR can be any alkyl group. Although R and R can be identical, they are usually

different.

Contrary to amines, most esters have pleasantodors. Many flowers and ripe fruits have fragrances and

tastes due to one or more esters.

Section 14.4


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Natural flavors are generallycomplex mixtures of esters andother constituents

Section 14.4


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Formation of an Ester Ester formation the reaction of a carboxylic acid

and an alcohol give an ester and water

Heat is required and sulfuric acid is a catalyst.

Note, in this reaction that theOH from the carboxylicacid unites with the H from the alcohol to form H2O.

The remaining two fragments bond together to form theester.

Section 14.4 Writing an Equation for


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Ester FormationAn Example Complete the equation for the sulfuric

acid-catalyzed reaction between acetic

acid and ethanol.



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Ester FormationAn Example (cont.) Lasso theOH from the acetic acid and the H

from the ethanol to form H2O.

Attach the remaining acid and alcohol

fragments together forming ethyl acetate.

Section 14.4 y ce a e o ecu e


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An ester used as a solvent inlacquers and other protectivecoatings

Insert figure 14.17, p.386, 11/e

From Ebbing, General Chemistry, 6th Ed. Section 14.4


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Fats Fats are a type of ester formed by the

combination of the trialcohol named

glycerol and fatty acids. Glycerol is CH2(OH)CH(OH)CH2(OH)

Stearic Acid (C17H35COOH) is found in beef

fat, and is a typical fatty acid.

Section 14.4


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Fats Generally fats from animals are solid at

room temperature.

Fats from plants and fish are generallyliquid at room temperature.

Liquid fats are referred to as oils.

Section 14.4


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Hydrogenation Liquid fats contain double bonds between

some of the carbon atoms.

These liquids fats are termed unsaturated.

Hydrogenation is the process of adding H to

the C atoms that have a double bond.

The hydrocarbon chains become saturated or nearly

saturated and the liquid fat is changed to a solid.

A common example of hydrogenation is the

reaction cottonseed oil to margarine.

Section 14.4 y rogena on


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When Cottonseed Oil (liquid) ishydrogenated, Margarine (solid) isthe result.

Section 14.4


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Soaps Soap the sodium slats of fatty acids

Soap is formed by reacting a fat with

sodium hydroxide (NaOH, lye.) The ester bonds break giving rise to

glycerol and sodium salts of the fatty

acids. Sodium stearate is a typical soap.

Section 14.4


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Soap Like Dissolves Like Generally we want to dissolve stains made by

nonpolar compounds such as grease.

The polar end of the soap dissolves in water. The other end of the soap molecule is long and

nonpolar.

This nonpolar end dissolves in the grease.

The emulsified grease droplets can be rinsed away.

Section 14.4 The long nonpolar chains


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of the detergent moleculedissolve the grease.

Section 14.4


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Amides Amides are nitrogen-containing organic

compounds with the general formula

RCONHR.

Section 14.4


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Amide Formation Amide formation is similar to ester formation.

A carboxylic acid reacts with an amine to form

water and an amide, as shown below.



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Amide FormationAn Example Complete the equation for the reaction to

form Phenacetin.

Section 14.4 r ng an qua on or


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Amide FormationAn Example (cont.)

Lasso theOH from the acid and the H fromthe amine to form H2O.

Attach the remaining acid and amine fragments

together forming Phenacetin.

Section 14.4


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Amino Acid Amino acids are organic compounds that

contain both an amino and carboxyl group.

Glycine and alanine are the simplest amino

acids. Proteins are extremely long polyamides,

formed by the condensation of amino acids. Proteins can range from a few thousand formula

units (insulin) to several million formula units. Proteins serve as both structural components and

enzymes.

Section 14.4

Linking Amino Acid


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Molecules Glycine and alanine react to form water and

another amino acid. This process can be repeated, eventually forming a

protein.

Section 14.4 and their


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DerivativesNames andGeneralFormulas

Section 14.4


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Synthetics Attempts to duplicate nature have long been a

goal of chemists.

Basic formulas and structures became known

as the science of chemistry progressed. As attempts were made to synthesize natural

compounds, synthetic compounds werecreated.

Synthetics are materials whose moleculeshave no duplicate in nature.

Section 14.5


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Synthetic Polymers The first synthetic polymer was prepared by

Leo Baekeland in 1907.

Commercially this substance was used as an

electrical insulator, called Bakelite. Chemists soon discovered that only slight

substitutions to a molecule could create newsubstances with very different properties.

Knowing the chemical properties of the originalmolecules and the substitutes allowed chemists topredict the resulting properties.

Section 14.5


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Synthetic Polymers Due to the scientific approach, chemists

were able to tailor new molecules for

specific purposes.

Plastics are probably the best known of

this group of synthetic polymers.

They can be molded and hardened formany different purposes.

Section 14.5


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Synthetic Polymers A polymer is a compound of very high

formula mass whose long chain

molecules are made of repeating units.

Monomer is the fundamental repeating

unit of a polymer.

There are two major types of polymers:Addition polymers

Condensation polymers

Section 14.5


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Addition Polymers Addition polymers are formed when molecules

of an alkene monomer add to one another.

Recall that alkenes have a double bond

between two carbon atoms. Under the proper reaction conditions the

double bond opens up and attaches itself bysingle bonds to two other monomer molecules.

Each of these monomers will then in turnattach to another monomer, and so on andon

Section 14.5


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Polymerization of Ethene

The subscripted n on polyethyleneindicates that the unit shown in bracketsis repeated thousands of times.

Polyethylene is the simplest of the

synthetic polymers. It is significantly inert chemically and is

used to make containers.

Section 14.5


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Teflon Teflon is made by the polymerization of

tetrafluoroethene.

This polymer is a hard, strong, chemicallyresistant compound with a high melting

point and very low surface friction.

Section 14.5 Drawing the Structure of


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an Addition Polymer - AnExample An addition polymer can be prepared from

vinylidene chloride, CH2==CCl2. Draw the

structure of the polymer.

To form the polymer the double bonds of all themonomers (CH2==CCl2) must open up and

repeatedly bond to the growing chain of

monomers.

The structure is shown as:

Section 14.5

Common


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AdditionPolymers

Section 14.5


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Condensation Polymers Condensation polymers are formed from

molecules of two or more reactive

groups.

Water is the other product, hence the name

condensation polymers.

Polyethylene terephthalate (PET) is

formed from the polymerization of

tetephthalic acid and ethylene glycol.

Section 14.5

Nylon A Condensation


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Polymer

Nylon was first introduced to the public in1939 at the New York Worlds Fair.

Nylon is formed from the polymerization of

adipic acid and hexamethylenediamine.

Section 14.5


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Velcro Velcro is a popular fastener made of

nylon.

The hooks of one surface entangle theloops of the other surface.

Section 14.5


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