organic chemistry: chemistry of carbon compounds

Organic Chemistry:

Chemistry of Carbon Compounds

Why so many C compounds?

• Carbon atoms can bond with other carbon atoms in chains, rings, and networks.

• Bonds are covalentcovalent.

Lewis Diagram of C

•• C •

•

Carbon has 4 unpaired electrons. It can form 4 covalent bonds.

Bonding Capacity of H, O, etc.

• H can form only 1 bond.

• O and S like to form 2 bonds.

• The halogens (F, Cl, Br, I) form only 1 bond.

• N and P form 3 bonds.

Properties of Covalent Substances

(also called molecularmolecular substances)

• Low melting & boiling points

• Poor conductors of heat & electricity

• May be soft or brittle

• Generally nonpolar

• Tend to dissolve in nonpolar solvents

• React more slowly than ionic compounds

Chemical FormulasChemical Formulas

• show kind & number of atoms.

CH4, CH3OH, CH3Cl, CH2Cl2

Structural FormulasStructural Formulas

• Show kind & number of atoms.• Also show bonding patterns and

approximate shapes of molecules.• 2-D rep of 3-D object so structural formulas

aren’t totally realistic. H

H–C–H H

Structural Formulas

• – A single line represents one pair of electrons (a single bond).

• = A double line represents two pairs of electrons (a double bond).

A triple line represents three pairs of electrons (a triple bond).

Shape

• The 4 unpaired electrons around the C atom are located at the corners of a tetrahedron.

• 109.5 apart.

Vocabulary Interlude

• SaturatedSaturated: organic compounds containing only single bonds.

• UnsaturatedUnsaturated: organic compounds containing one or more double or triple bonds.

Vocabulary

• HydrocarbonsHydrocarbons: organic compounds containing only C and H.

• Homologous SeriesHomologous Series: a group of compounds with related structures and properties. Each member of the series differs from the one before it by the same additional unit.

Condensed Structural FormulaCondensed Structural Formula

• Shows kind & number of atoms

• Shows some structural information, but not all the details.

H H H

H–C–C–C–H

H H H

Becomes CH3CH2CH3

Alkanes• Homologous series of saturated hydrocarbons.• Release energy when burned.

CH4 H H–C–H

H

C2H6 H HH–C–C–H H H

• Or CH3CH3

Alkanes or CnH2n+2

• C3H8

H H H

H–C–C–C–H

H H H

CH3CH2CH3

4th straight-chain alkane

C4H10

H H H H

H–C–C–C–C–H

H H H H

Or CH3CH2CH2CH3

Alkanes: base unit

CH4

CH3CH3 or C2H6

CH3CH2CH3 or C3H8

CH3CH2CH2CH3 or C4H10

CH3CH2CH2CH2CH3 or C5H12

Difference between each is CHCH22

Naming straight-chain Alkanes

• All alkaneanes have the suffix –aneane.

• The prefix depends on the number of C’s.

Prefix # of C atoms

Meth 1

Eth 2

Prop 3

But 4

Pent 5

Hex 6

Hept 7

Oct 8

Non 9

Dec 10

Formula NameCH4 Methane

C2H6 Ethane

C3H8 Propane

C4H10 Butane

C5H12 Pentane

Properties of Alkanes

• Change systematically with number of C’s

• As the number of C’s increases, the boiling point increases.

Branched-chain alkanes

• Beginning with butane, C4H10, there is more than 1 way to arrange the atoms.

H

H–C–H

H H

H–C–C–C–H

H H H

Isomers

• Compounds with the same molecular formula but different structural arrangement, and therefore, different chemical properties.

• The more C atoms there are in the formula, the more isomers there will be. More possible ways to arrange them.

Isomers

• Different structures, different properties.

• Isomers have different chemical and physical properties.

Naming branched-chain alkanes• Find the longest continuous chain or backbone of C atoms.

(Bends don’t count!)• The base name is derived from the number of C’s in the

longest chain.• Branches are named in the prefix. Branches are also named

by the number of C atoms. The “branch” part of the name ends in “yl.”

• The location of the branch is shown by assigning numbers to the C’s in the backbone. Number from the end that gives the lowest number for the branch.

• There may be more than 1 of the same type of branch. Use di, tri, etc.

H

H–C–H

H H

H–C–C–C–H

H H H

Longest continuous chain has 3carbon atoms – propane.Branch has 1 carbon – methyl.Branch has to be at C-2.(Only give the number if necessary.)

Methyl propane

C4H10

CH3CH(CH3)CH3

HH–C–H

H–C–H H H HH–C–C–C–C–H H H H H–C–H H

Longest continuous chain has 6 carbon atoms. It’s a hexane.Branch is 1 carbon long – methyl.Branch is located at C-2.

2-methyl hexane

C7H16

CH3CH(CH3)CH2CH2CH2CH3

H

H – C – H

H H HH – C – C – C – C – H H H H–C–H H–C–H H H

Longest continuous chain has 6 carbon atoms: hexaneBranch is 1 carbon long: methylBranch is located at C-3

3-methyl hexane

C7H16

CH3CH2CH2CH(CH3)CH2CH3

CH3(CH2)2CH(CH3)CH2CH3

Alkenes

• Another homologous series of hydrocarbons hydrocarbons.

• Each member contains oneone double covalent bond between C atoms.

So alkenes are unsaturatedunsaturated.

• General formula = CnH2n

Naming Alkenes

• Names are derived from the name of the alkane chain with the same number of C atoms. Replace the –ane ending of the alkane name with –ene.

1st member is C2H4, ethene.

H HH HCC=C=C

H H H H

Naming Alkenes• Location of double bond is specified by

numbering C atoms in backbone. Give bond the lowest possible number.

H H H C=C–C–C–HH H H H

C4H8

CH2CHCH2CH3

H H H HH–C–C=C–C–H H H

C4H8

CH3CHCHCH3

1-butene 2-butene

Naming Branched-Chain Alkenes

• Parent chain = longest chain that contains the double bond.

• Also, position of double bond, not branches, determines numbering of backbone.

• Give 1st C in bond lowest possible #.

Alkynes• Homologous series of unsaturated

hydrocarbons that contain one triple bond.

• Each member contains one triple carbon-carbon bond.

– Alkynes are unsaturated.

• General formula = CnH2n-2

Naming Alkynes

• Use the corresponding name from the alkane series and change the –ane to –yne.

• If necessary, number the carbon atom at which the triple bond occurs.

H–CC–H C2H2 ethyne CHCH

HH–CC–C–H C3H4 propyne CHCCH3

H

H HH–CC–C–C–H C4H6 1-butyne CHCCH2CH3

H H

H HH–C–CC–C–H C4H6 2-butyne CH3CCCH3

H H

Organic Halide

• One or more of the hydrogen atoms in an alkane is replaced with a halogen (F, Cl, Br, or I).

• NotNot hydrocarbons! Often called halocarbons.• Use prefixes to specify substituent: fluoro, chloro,

bromo, iodo• If more than one, use di, tri, etc. to specify # of

substituents.• If necessary, give locations by numbering C-atoms

in backbone.

Naming Halides

CH3Cl CH3CHFCH3

HH–C–Cl H

chloromethane

H H HH–C–C–C–H H F H

2-fluoropropane

C3H7F

Naming Halides

CH3CCl2CHClCH3

H Cl Cl H H

H – C C – – C C – – C C – – CC – H H Cl ClCl Cl H

2,2,3-trichlorotrichlorobutanebutane

C4H7Cl3