Organic Chemistry: Chemistry of Carbon Compounds

Why so many C compounds? Carbon atoms can bond with other carbon atoms in chains, rings, and networks. covalentBonds are covalent.

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 molecular (also called molecular 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 Formulas show kind & number of atoms. CH 4, CH 3 OH, CH 3 Cl, CH 2 Cl 2

Structural 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  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 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 CH 3 CH 2 CH 3

Alkanes Homologous series of saturated hydrocarbons. Release energy when burned. CH 4 H H–C–H H C 2 H 6 H H H–C–C–H H H Or CH 3 CH 3

Alkanes or C n H 2n+2 C 3 H 8 H H H H–C–C–C–H H H H CH 3 CH 2 CH 3

4 th straight-chain alkane C 4 H 10 H H H–C–C–C–C–H H H Or CH 3 CH 2 CH 2 CH 3

Alkanes: base unit CH 4 CH 3 CH 3 or C 2 H 6 CH 3 CH 2 CH 3 or C 3 H 8 CH 3 CH 2 CH 2 CH 3 or C 4 H 10 CH 3 CH 2 CH 2 CH 2 CH 3 or C 5 H 12 CH 2 Difference between each is CH 2

Naming straight-chain Alkanes aneaneAll alkanes have the suffix –ane. The prefix depends on the number of C’s.

Prefix# of C atoms Meth1 Eth2 Prop3 But4 Pent5 Hex6 Hept7 Oct8 Non9 Dec10

FormulaName CH 4 Methane C2H6C2H6 Ethane C3H8C3H8 Propane C 4 H 10 Butane C 5 H 12 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, C 4 H 10, there is more than 1 way to arrange the atoms. H H–C–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–C–C–C–H H H H Longest continuous chain has 3 carbon atoms – propane. Branch has 1 carbon – methyl. Branch has to be at C-2. (Only give the number if necessary.) Methyl propane C 4 H 10 CH 3 CH(CH 3 )CH 3

H H–C–H H H H H–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 C 7 H 16 CH 3 CH(CH 3 )CH 2 CH 2 CH 2 CH 3

H H – C – H H H H H – C – C – C – C – H H H H–C–H H–C–H H H Longest continuous chain has 6 carbon atoms: hexane Branch is 1 carbon long: methyl Branch is located at C-3 3-methyl hexane C 7 H 16 CH 3 CH 2 CH 2 CH(CH 3 )CH 2 CH 3 CH 3 (CH 2 ) 2 CH(CH 3 )CH 2 CH 3

Alkenes hydrocarbonsAnother homologous series of hydrocarbons. one unsaturatedEach member contains one double covalent bond between C atoms.  So alkenes are unsaturated. General formula = C n H 2n

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. 1 st member is C 2 H 4, ethene. H H 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–H H H C 4 H 8 CH 2 CHCH 2 CH 3 H H H H H–C–C=C–C–H H H C 4 H 8 CH 3 CHCHCH 3 1-butene2-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 1 st 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 = C n H 2n-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–C  C–HC 2 H 2 ethyneCHCH H H–C  C–C–HC 3 H 4 propyneCHCCH 3 H H H H–C  C–C–C–HC 4 H 6 1-butyneCHCCH 2 CH 3 H H H–C–C  C–C–HC 4 H 6 2-butyneCH 3 CCCH 3 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 CH 3 ClCH 3 CHFCH 3 H H–C–Cl H chloromethane H H H H–C–C–C–H H F H 2-fluoropropane C3H7FC3H7F

Naming Halides CH 3 CCl 2 CHClCH 3 Cl H Cl H H C – C – C – C H – C – C – C – C – H Cl Cl H trichlorobutane 2,2,3-trichlorobutane C 4 H 7 Cl 3