Organic ChemistryOrganic Chemistry

Unit 10

What is Organic Chemistry?Organic chemistry

is the study of carbon compounds.

Besides carbon, the most common elements in organic compounds are hydrogen, oxygen, nitrogen, sulfur, and the halogens.

Why is it Important?Animals, plants, and other forms of life

consist of organic compounds.Organic products are found in foods,

drugs, clothing, fuel, and many other products that we use everyday.

Organic chemistry is an enormous field.o >90% of all

compoundsare organic.

History of Organic Chemistry

Scientists originally thought organic compounds contained a “vital force” due to their natural origin.

Until 1828, when Friedrich Wöhler made urea (found in human urine) in the lab from a mineral.

Today, many organic compounds are synthesized in the laboratory.

Bonding in Organic CompoundsOrganic compounds are made of all non-

metals, so they have covalent bonding.Their structures almost always obey the

bonding rules in the following table:

Why Carbon is UniqueCarbon forms 4 covalent bonds with a

number of different elements, resulting in many different compounds.

Carbon atoms readily form multiple bonds.Carbon, more than any other element,

displays catenation – the ability of an atom to form stable bonds with itself, joining up into chains or rings.

CnH2n+2 n = 1to (no limit)SinH2n+2 n = 1 to 6 onlyGenH2n+2 n = 1 to 3 onlySnnH2n+2 Only SnH4 exists

Representing Organic CompoundsStructural Formulas show all of the

carbon and hydrogen atoms and how they are bonded together.

Line-Angle (Carbon Skeleton) formulas do not show the hydrogen atoms that are bonded to carbons. Each angle, and beginning and end of a line, represents a carbon atom.

Space-filling and ball-and-stick models are three-dimensional representations of the molecule.

Formulas

IsomersIsomers are different molecules with

the same molecular formula.o Structural Isomers (aka

Constitutional Isomers) have a different pattern of atom attachment.

o Stereoisomers have the same atom attachments, but a different spatial orientation.

Structural (Constitutional) IsomersCompounds with the same molecular

formula but different structural formulas.Ex: n-butane and isobutane both have

the molecular formula of C4H10 but their structural formulas are quite different.

C4H10n-butane C4H10isobutane

StereoisomersDifferent molecules whose atoms are

connected in the same order, but have a different spatial orientation.o optical isomers –

nonsuperimposable mirror images.

o Geometric (cis-trans) isomers – cis means “same side”, trans means “opposite side”.

IsomersSample Problem

Write line-angle (carbon skeleton) formulas for the five isomers of C6H14.

Use lines to represent each carbon-carbon bond. Remember that each end or bend represents a carbon atom.

HydrocarbonsHydrocarbons are the simplest organic

compounds, containing only carbon and hydrogen.

However, due to theuniqueness of carbon,there are many different kinds of hydrocarbons.

Hydrocarbons are commonly used as fuels, and are the starting materials in the synthesis of many consumer products.

AlkanesAlkanes are hydrocarbons that contain only

single bonds.Alkanes are said to be

saturated, because theirhydrogen content is at a maximum.

Names all end in “-ane.”General formula is CnH2n + 2

Methane - butane are gases, Pentane - C17H36 are liquids, C18H38 & higher are solids.

Alkanes tend to be stable molecules, and not very reactive (other than combustion.)

IUPAC NomenclatureSince there are so many organic

compounds, a systematic methodof nomenclature is required.

The system recommended by IUPAC (International Union of Pure and Applied Chemistry) is used throughout the world.

Each name consists of 3 parts:o Prefixo Parento Suffix

2,5-dimethylhexane

prefix

parent(base)

suffix

Numbering the Base Chain Find the longest continuous

carbon chain. Number the chain

from the end closest to a branch (substituent.)

o If 2 first branches are at equal distances from each end, use the next branch in to determine where to start.

Use the appropriate base prefix, followed by the suffix-ane for an alkane.

XIncorrect

XIncorrect

Alkyl GroupsName branches (substituents) as alkyl

groups – carbon-hydrogen groups with one less H than the corresponding alkane.

The group does not exist independently but occurs bonded to another atom or molecule.

In naming, the “-ane” is droppedand “-yl” is added. Ex: methane becomes methyl.)

Substituentsa substituent is an atom or group of

atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon.

Common substituents, other than alkyl groups, are oxygen, sulfur or nitrogen-based groups, and the halogens.

Naming Substituents Locate each substituent by preceding its

name with the carbon number on the chain

List branches alphabetically

o do not count n-, sec-, t-, count iso

Use prefix if morethan one of samegroup present (Ex: di, tri, tetra, penta)

o Prefixes do not count in alphabetizing

1 2 3 4

5 6 7 8

9

nonane5-ethyl-4-isopropyl-

4-methyl

Naming AlkanesSample Problem

Write the correct IUPAC names for the following organic compounds:a.)

b.)

12

34

12

34

56

7

89

butane

2,2,3-trimethyl

1-bromo-

nonane

2,5,5,7-tetramethyl

3-ethyl-

CycloalkanesCycloalkanes have rings of carbon

atoms.They have the general formula CnH2n

In carbon skeleton formulas, assume a C atom at each corner and enough H’s to give a total of 4 single bonds to each C.

Naming CycloalkanesThe ring is named by the number of carbons

(as before) but with the prefix cyclo-.Number the ring starting from the carbon

with the substituent lowest in the alphabet. Number in the direction

that gives the lower overall substituent numbers. (To breaka tie, go in the direction that is alphabetical).

Write the correct IUPAC names for the following organic compounds:a.)

b.)

Naming CycloalkanesSample Problem

1

23

4

1

23

45

65

cyclohexane

chloro

cyclopentane

3-methyl

1-isopropyl-

Alkenes & AlkynesAlkenes have a double bond between 2

carbon atoms. General formula is CnH2n.Alkynes have a triple bond between 2

carbon atoms. General formula is CnH2n-2.Called unsaturated hydrocarbons since

they’re not loaded to capacity with H.Much more reactive than alkanes.

Naming Alkenes & AlkynesChange suffix from

-ane to -ene for base name of thealkene, or to -yne for base name of the alkyne.

Number chain fromend closest to the multiple bond.

Number in front of main name indicates first carbon of multiple bond.

Write the correct IUPAC names for the following organic compounds:a.)

b.)

Naming Alkenes & AlkynesSample Problem

1 2 3 4 5 62-hexyne

4-methyl-

2-butene

trans-

1

2 3

4

Classification of HydrocarbonsAll of the hydrocarbons we have looked

at so far are called aliphatic.There is another classification, called

aromatic, which includes any hydrocarbon containing a benzene ring.

BenzeneThe benzene molecule is

composed of 6 carbon atoms joined in a ring, with 1 hydrogen atom attached to each carbon atom (C6H6.)

A six-membered ring of carbon atoms with alternating single and double bonds was proposed for the structure of benzene by August Kekulé in1865.

However, properties of the benzene molecule and advanced bonding theory indicate that the electrons are actually shared by all the carbon atoms in the ring.

Benzene (cont’d.)

Aromatic CompoundsAromatic hydrocarbons

contain one or more benzene rings.

Although they are often drawn with C=C bonds, they do not behave like alkenes.

Many of these compounds have distinctive, often pleasant, aromas.

when the benzene ring isnot the base name, it is called a phenyl group

Write the correct IUPAC names for the following organic compounds:a.)

b.)

Naming Aromatic CompoundsSample Problem

1

2

3

4

5

6

benzene2,6-dichloro

octane

1-phenyl

12

34

56

78

1-bromo-

Functional GroupsA functional group is a characteristic atom or

group of atoms inserted into a hydrocarbon.The presence of a

functional groupalters the propertiesof a compound, and determines thereactions it will participate in.

since the type of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol R

nonpolargas

polar, H-bondedliquid

Alcohols are organic compounds containing a hydroxyl group(-OH).

General formula is R-OH. IUPAC names end in -ol.

Number the main chain from the end closest to -OH. Include the number of the -OH group.

-OH groups are able to form hydrogen bondswith H2O, but the longer the hydrocarbon chain, the less soluble the alcohol is in water.

Alcohols

Ethers are organic compounds with the general formula ROR.

Diethyl ether is a common labsolvent, and was used as a general anesthetic.

To name ethers, name each alkyl group attached to the O,then add ether to the end. List the R groups in alphabetical order. If they are the same, use di-.

Ethers

Aldehydes and KetonesBoth aldehydes and ketones

contain the carbonyl group.Ketones have an R group

attached to both sides ofthe carbonyl group. IUPAC names end in -one.

Aldehydes have at least one H atom attached to the carbonyl group. IUPAC names end in -al.

Aldehydes and Ketones (cont’d)

Many aldehydes and ketones have pleasant tastes and aromas.

Some are pheromones. Cinnamaldehyde3-phenyl-2-propenal

Raspberry Ketone4-(4-hydroxyphenyl)butan-2-

one

Carboxylic Acids and EstersCarboxylic acids have the general

formula RCOOH. Their IUPAC names end in -oic acid.

Esters have the general formulaRCOOR’. Their IUPAC names arebased on the corresponding carboxylic acid. Change the -ic acid ending to -ate. The R group replacing the H is named as an alkyl group.

Carboxylic Acids and Esters (cont’d)

Carboxylic acids are weak acids. Like all acids, they taste sour.

Esters are best known for their sweet smells.

Citric Acid2-hydroxypropane-1,2,3-tricarboxylic

acid

Acetic AcidEthanoic acid

Methyl Butanoate Ethyl Butanoate

An amine is an organic compoundthat contains nitrogen, and can be thought of as a derivative of ammonia.

Like ammonia, amines areweak bases.

Amines form when proteins decompose, and are known for their awful odors.

Name the alkyl groups attached to the N, then add -amine to the end.

Amines

Write the correct IUPAC names for the following organic compounds:a.)

b.)

Naming w/ Functional GroupsSample Problem

12 ethe

rphenyl

propanoic acid

2-methyl123

ethyl

Write the correct IUPAC names for the following organic compounds:c.)

d.)

Naming w/ Functional GroupsSample Problem (Continued)

amine

2-hexanol

3-methyl-12

34

5 6

trimethyl

Types of Organic ReactionsOrganic compounds participate in 3 main

types of chemical reactions:o Substitution – atom(s) of

the starting material are replaced by other atom(s).

o Elimination - atoms of thestarting material are“lost” and a new bond is formed.

o Addition - atoms areadded to the starting material.

Substitution ReactionsSubstitution reactions involve bonds:

one bond breaks and another forms at the same carbon atom.

The atom being replaced is usually either a hydrogen or another atom more electronegative than carbon.

Elimination Reactions In an elimination reaction, 2 groups (X & Y)

are removed from a starting material.Two bonds are broken, and a bond is

formed between adjacent atoms.Most often, X is hydrogen and Y is an atom

more electronegative than carbon.

Addition Reactions In an addition reaction, 2 new groups (X &

Y) are added to the starting material. A bond is broken and 2 bonds are formed.

Addition and elimination reactions are exact opposites. A bond is formed in elimination, and broken in addition.

Classify each of the following as either substitution, elimination or addition reactions:

a.)

b.)

c.)

Types of Organic ReactionsSample Problem

addition

elimination

substitution

OHBr

OH

PolymersPolymers are long, chainlike

molecules composed of repeating units.

A monomer is the fundamental repeating unit of a polymer.

Natural PolymersNatural Polymers play an important

role in living organisms.Examples: starches,

proteins, and DNA.

Synthetic PolymersSynthetics are man-made

materials that have no duplicate in nature.

The first synthetic polymer wasprepared by Leo Baekeland in 1907.

Due to the scientific approach, chemists have been able to tailor new molecules for specific purposes.