Post on 05-Jan-2016
transcript
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