Organic ChemistryDP Chemistry

What is Organic Chemistry?

“Organic” is a term that is used in a variety of ways:

“from living things” “chemical free” “carbon-based”

Organic Chemistry is the study of carbon-based compounds

Carbon Carbon is in Group IV of the

periodic table

Carbon has 4 valence electrons

Carbon can form 4 covalent bonds

Carbon can form single, double and triple bonds with a wide variety of elements forming nearly ten million known compounds

1s2 2s2 2p2

C12

6

Tetravalent CarbonBecause carbon has four

valence electrons, it forms four bonds with other elements to make up a full valence shell of 8. All valence electrons are involved in bonding.

This bonding leads to tetrahedral shapes when all of the bonds involved are single bonds.

Hydrocarbons are made up of carbon bonded to hydrogen, but many elements can and do take the place of hydrogen.

Common elements that bond to carbon are N, O, S and the halogens (e.g. Cl, F).

Methane CH4

Carbon tetrachloride CCl4

Carbon atom

Chlorine atoms

Carbon atomHydrogenatoms

Carbon Bonding

C C

H

H

H H

H

H

C CH

H

H

H

Single bond - ethane

Double bond - ethene

C2H6

C2H4

Structural Formula

Molecular Formula

Carbon Bonding

C CH HTriple bond – ethyne(acetylene)

C2H2

Structural Formula

Molecular Formula

Cyclic– benzene C6H6

Fractional DistillationCrude oil contains a

mixture of hydrocarbons ranging from one carbon (C1) up to more than C24.

Fractional distillation allows for these components or ‘fractions’ to be separated using a fractionating column.

In this process, heat is applied to the bottom of the column and lighter compounds with lower boiling points rise to the top, while heavier compounds remain towards the bottom of the column.

Source: http://www.bbc.co.uk/schools/gcsebitesize/chemistry/usefulproductsoil/oil_and_oilproductsrev5.shtml

HydrocarbonsAlkanes - hydrocarbons that contain only single bonds (all bonds and no bonds - saturated). The table to the right shows the alkane homologous series (a family of compounds that have the same general formula differing by CH2).

Formula – CnH2n+2

Straight-chain alkanes – carbons joined together to form a single chain with no branching.

Number of C Alkane

1 Methane

2 Ethane

3 Propane

4 Butane

5 Pentane

6 Hexane

7 Heptane

8 Octane

Methane Ethane Propane Butane

Structural formulae

HydrocarbonsAlkenes – hydrocarbons that

contain one double bond between two carbon atoms.

Formula – CnH2n

Isomers – compounds that have the same molecular formula, but different structure.

Alkenes have isomers because the double bond can be in a different location above C4. The location of the double bond is indicated by a numerical prefix counting from the shortest end.

Number of C Alkene

1 NA

2 Ethene

3 Propene

4 Butene

5 Pentene

6 Hexene

7 Heptene

8 Octene

CH CH3CH2CH2 CH CH3CH2CH2 CH2 CH CH3CHCH2 CH2

1-butene 1-pentene 2-pentene (NOT 3-pentene)

Condensed structural formulae

Hydrocarbons

Alkynes – hydrocarbons that contain one triple bond between two carbon atoms.

Formula – CnH2n-2

Number of C Alkyne

1 NA

2 Ethyne

3 Propyne

4 Butyne

5 Pentyne

6 Hexyne

7 Heptyne

8 Octyne

As with alkenes, a numerical prefix indicates the location of the triple bond.

Alkane b.p. trendAs alkanes get larger in size, the intermolecular forces increase due to a greater amount of dispersion forces.

The table below and graph to the right show the trend in boiling point for simple, straight-chain alkanes.

The longer the chain, the greater the forces between molecules

Types of FormulaeMolecular Structural Formula Condensed Structural

4 Types:

1. Empirical –this shows the ratio of elements in the compound

2. Molecular – shows the actual number of atoms in a compound, but no information about how they are arranged

3. Structural – shows the arrangement of elements and all of the bonds between them. Most appropriate

4. Condensed Structural – omits some or all of the bonds and may show identical groups bracketed together. These are not acceptable when asked for a structural formula.

e.g. CH3(CH2)4CH3

Structural Isomers

Structural isomers are molecules that have the same molecular formula, but different structures.

Butane

Molecular formula: C4H10

Notice that changing the structure, changes some of the physical properties

Structural Isomers

PentaneNotice again that changing the structure, changes some of the physical properties. What pattern do you notice with these isomers?M.p./b.p. decreases with more

branching

Naming HydrocarbonsExamples of Simple Unbranched Alkanes

Name MolecularFormula

StructuralFormula Isomers Name Molecular

FormulaStructuralFormula Isomers

methane CH4 CH4 1 hexane C6H14 CH3(CH2)4CH3 5

ethane C2H6 CH3CH3 1 heptane C7H16 CH3(CH2)5CH3 9

propane C3H8 CH3CH2CH3 1 octane C8H18 CH3(CH2)6CH3 18

butane C4H10 CH3CH2CH2CH3 2 nonane C9H20 CH3(CH2)7CH3 35

pentane C5H12 CH3(CH2)3CH3 3 decane C10H22 CH3(CH2)8CH3 75

IUPACIUPAC – The International Union of Pure and Applied Chemistry is a group of Chemists who devised a system of naming that allows for unique names to be applied to organic compounds. There are many compounds that also have common names, but this system allows us to speak a common language when naming these compounds. The simple alkanes above are the simplest examples.

IUPAC - Naming hydrocarbonsProblemHexane C6H14 has 5 isomers. (See right)

How do we distinguish between them?

IUPAC “Quick” Rules for Alkane Nomenclature1. Find and name the longest continuous carbon chain. 2.   Identify and name groups attached to this chain. (These are called substituents.)3.   Number the chain consecutively, starting at the end nearest a substituent group. 4.   Designate the location of each substituent group by an appropriate number and name.5.   Assemble the name, listing groups in alphabetical order using the full name (e.g. ethyl before methyl). The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing.

Note: these are shorthand notations where each line represents a bond between two carbon atoms

Important notes: • a hydrocarbon substituent becomes an alkyl group. (e.g. ethane becomes ethyl)• Some substituents are “active sites” for reactions to occur (e.g. alcohols, ketones, alkenes) –

these are then also referred to as functional groups.

IUPAC names for the isomers?

IUPAC “Quick” Rules for Alkane Nomenclature1. Find and name the longest continuous carbon chain. 2.   Identify and name groups attached to this chain. (These are called substituents.)3.   Number the chain consecutively, starting at the end nearest a substituent group. 4.   Designate the location of each substituent group by an appropriate number and name.5.   Assemble the name, listing groups in alphabetical order using the full name (e.g. ethyl before methyl). The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing.

n-hexane 2,3 – dimethyl butane

2,2 – dimethylbutane

3-methyl pentane

2-methyl pentane

IUPAC – Naming AlkenesIUPAC Rules for Alkene and Cycloalkene Nomenclature1.   The ene suffix (ending) indicates an alkene or cycloalkene.2.   The longest chain chosen for the root name must include both carbon atoms of the double bond. 3.   The root chain must be numbered from the end nearest a double bond carbon atom. If the double bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.4.   The smaller of the two numbers designating the carbon atoms of the double bond is used as the double bond locator. If more than one double bond is present the compound is named as a diene, triene or equivalent prefix indicating the number of double bonds, and each double bond is assigned a locator number.5.   In cycloalkenes the double bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule.6.   Substituent groups containing double bonds are:            H2C=CH–   Vinyl group            H2C=CH–CH2–   Allyl group

But-1-ene

But-2-ene

Functional Groups Functional groups are specific groups of atoms or bonds within a compound that are responsible for characteristic chemical properties of those substances.

Amines, Amides, Esters and Nitriles are HL only

Alcohols

R-OHAlcohols contain the hydroxyl group (OH) in place of a H atom in a hydrocarbon.

Formula – CnH2n+1OH

Compound suffix – “anol”

A number is used to indicate the location of the hydroxyl on a carbon chain in the same manner previously described.

Alcohols follow the same trend in b.p. as the hydrocarbons, but are all higher due to H-bonding.

Formula Name

CH3OH Methanol

CH3(CH2)OH Ethanol

CH3(CH2)2OH Propanol

CH3(CH2)3OH Butanol

CH3(CH2)4OH Pentanol

CH3(CH2)5OH Hexanol

Propan-1-ol

Aldehydes

R-CHOAldehydes contain the carbonyl group (C=O) which is bonded to the last (terminal)carbon in a chain.

Formula – CnH2nO

Compound suffix – “anal”

No numbers are necessary for the naming of aldehydes as the group is on the terminal carbon.

Because of the carbonyl, there are permanent dipoles leading to stronger IM forces than alkanes, but weaker than alcohols.

Formula Name

HCHO Methanal

CH3CHO Ethanal

CH3CH2CHO Propanal

CH3(CH2)2CHO Butanal

CH3(CH2)3CHO Pentanal

CH3(CH2)4CHO Hexanal

Propanal

Ketones

R-COR’Ketones contain the carbonyl group (C=O) which is bonded to a carbon that is not on the terminal end. This placement is how they differ from aldehydes.

Formula – CnH2nO

Compound suffix – “anone”

A number is used to indicate the location of the carbonyl on a carbon chain.

Because of the carbonyl, there are permanent dipoles leading to stronger IM forces than alkanes, but weaker than alcohols.

Formula Name

CH3COCH3 Propanone

CH3(CH2)COCH3 Butanone

CH3(CH2)2COCH3 Pentanone

CH3(CH2)3COCH3 Hexanone

Butan-2-one

Carboxylic Acids

R-COOHCarboxylic acids contain the carbonyl group (C=O) and the hydroxyl (OH) group.

Formula – CnH2nO2

Compound suffix – “anoic acid”

These compounds are polar towards the O atoms, away from the H atom, making the H atom available in acid/base rxns.

Because of the carbonyl and the hydroxyl, Hydrogen bonding occurs between these molecules.

Formula Name

HCOOH Methanoic acid

CH3COOHEthanoic acid

CH3CH2COOH Propanoic acid

CH3(CH2)2COOH Butanoic acid

CH3(CH2)3COOH Pentanoic acid

CH3(CH2)4COOH Hexanoic acid

Ethanoic acid

Halides

R-XHalogenoalkanes contain the halide functional group, which is a halogen (X)atom in place of a hydrogen.

Formula – CnH2n+1X

Compound prefixes – “chloro”, “bromo”, “iodo”

These compounds are named with the corresponding halogen atom at the beginning with the remainder of the compound named as per the rules for hydrocarbons.

Again, a number is used to indicate the position of the halogen on the carbon chain. More than one halogen may be present

Formula Name

CH3Cl chloromethane

CH3CH2Br Bromoethane

CH3(CH2)2I Iodopropane

CH3(CH2)3Cl Chloropropane

CH3(CH2)4Br Bromobutane

CH3(CH2)5I Iodohexane

2-chloropropane

Primary, Secondary, Tertiary alcohols and halides

Primary (10): When a functional group is attached to a carbon that is bonded to only one other carbon atom.

Secondary (20): When a functional group is attached to a carbon that is bonded to two other carbon atoms.

Tertiary (30): When a functional group is attached to a carbon that is bonded to 3 other carbon atoms.

For you to do:Name the three alkyl halides above

Other functional groups

Amino • R-NH2

Benzene ring• R-C6H5

Esters• R-COR’

What functional groups can you see?

IBUPROFEN

Carboxylic acid

Benzene ring

What functional groups can you see?

Carboxylic acid

Ester

What functional groups can you see?

Carboxylic acid Amine

An amino acid

Amines (AHL)

R-NH2

Amines contain the amino group (NH2) somewhere in the hydrocarbon chain.

Formula – RNH2

Compound suffix – “ylamine” ORCompound prefix – “amino”

A number is used to indicate the location of the amino on a carbon chain in the same manner previously described.

Formula Name

CH3NH2Methylamine or Aminomethane

CH3(CH2)NH2Ethylamine or Aminoethane

CH3(CH2)2NH2Propylamine or Aminopropane

1-butylamine

Amides (AHL)

R-CONH2

Amides contain the amino group (NH2) and a carbonyl group (C=O).

Formula – RCONH2

Compound suffix – “anamide”

Amides are the same structure as carboxylic acids with the amine group replacing the hydroxyl.

Formula Name

HCONH2 Methanamide

CH3CONH2 Ethanamide

CH3CH2CONH2 Propanamide

butanamide

Esters (AHL)

R-COOR’Esters contain the carbonyl group (C=O) with an additional O attached to the carbon.

Formula – RCOOR’

Compound suffix – “yl oate”

Esters are named in two parts from the carboxylic acid and alcohol that they are made from.

The first part of the name comes from the alcohol and the second from the acid.

Nitriles (AHL)

R-CNNitriles (aka cyanides) contain the cyano group which is a carbon triple bonded to a nitrogen.

Formula – RCN

Compound suffix – “nitrile”

Nitriles are named by their hydrocarbon chain with nitrile added at the end.

Formula Name

CH3CN Methanenitrile

CH3(CH2) CN Ethanenitrile

CH3(CH2)2CN Propanenitrile

pentanenitrile