Chapter 20 Organic Chemistry

Organic Compounds Organic compounds all contain carbon –CO, CO 2, carbonates are inorganic –Other common elements found in organic compounds are H, O, N, P, S The majority of the 50+ million known compounds are organic

What is so special about Carbon ? Structural Diversity Versatile bonding patterns –Chains, rings. multiple bonds –With 4 valence electrons, carbon can form 4 bonds to reach an octet with a variety of geometries 4 single bonds a double bond and two single bonds 2 double bonds A triple bond and a single bond

What is so special about Carbon? Structural Diversity Isomers: compounds having the same composition but different structures –Structural isomers –Stereoisomers Geometric isomers Optical isomers Site for viewing

What is so special about Carbon? Stability –Strong bonds C-C (346kJ/mol), C-H (413kJ/mol) Si-Si (222kJ/mol), Si-H (318kJ/mol) –C-C bonds unreactive (stable) Oxidation reactions are slow and these reactions need to be initiated

How are Carbon compounds represented Molecular formula : C 5 H 12 Condensed: CH 3 CH(CH 3 )CH 2 CH 3 Structural formula

Line-Bond Structures Shows only C-C bonds Ends of lines and corners are understood to be carbon atoms Proper number of hydrogens are understood Oxygens and nitrogens are shown

How are Carbon compounds represented Models –Ball and stick –Space filling

Hydrocarbons Alkanes: C n H 2n+2 –Unreactive –Saturated (all single bonds within compound)

Hydrocarbons: Alkanes Names end in “ane” Can form many structural isomers: same formula but atoms arranged differently –straight chain –Branched chain

Naming Alkanes Find the longest continuous carbon chain Number the chain from end closest to a branch Name branches as alkyl groups –Branch name related to number of C –End in -yl –Locate each branch by preceding its name with the carbon number on the chain

Naming Alkanes (cont.) List branches alphabetically Use prefix if more than one of same group present –di, tri, tetra, penta, hexa –Do not count in alphabetizing

Nomenclature: Alkanes n- pentane 2-methyl butane 2,2,dimethyl propane

Hydrocarbons: cycloalkanes C n H 2n

Alkenes Aunsaturated Formula of chain alkenes - C n H 2n C=C double bonds Much more reactive than alkanes Polyunsaturated = many double bonds

Alkenes (cont.) Trigonal shape around C –Flat No rotation –cis-trans isomerism

Alkenes: Cis Trans Isomerism Cis Trans

Naming Alkenes Change suffix on main name from -ane to –ene Number from end closest to double bond Number in front of main name indicates first carbon of double bond

Alkynes unsaturated Formula of chain alkynes - C n H 2n-2 C  C triple bond –Linear shape –No rotation More reactive than alkenes

Hydrocarbons: Alkynes

Aromatics Compounds that contain 1 more unsaturated rings –Benzene rings

Aromatics Benzene –All C-C bond lengths and bond angles identical 120° Bond lengths between C-C and C=C –Planar molecule

Functional Groups Alcohols Ethers Carboxylic acids Ketones Aldehydes Esters Amines Amides

Functional Groups In many organic compounds, C-to-H bonds are replaced by bonds to other atoms. –C-Halogen, C-to-O, C-to-N, occasionally (C-to-S) These substituted bonds are more reactive than C-H bonds. Have influences on intermolecular attractions and therefore physical properties

Functional Groups: Alcohols R-OH

Alcohols R-OH

Naming Alcohols Select the longest chain of carbon atoms containing the –OH group Number the chain from the end closest to the –OH group Determine the parent name from the number of C in the chain, replace the final - e with –ol Name alkyl branches as usual

Functional Groups: Ethers R-OR´

Ethers R-O-R′ contain an –O– between two carbon groups that are simple are named by listing the alkyl names in alphabetical order followed by ether CH 3 -O-CH 3 CH 3 -CH 2 -O-CH 3 Dimethyl ether Ethyl methyl ether

Functional Groups: Ketones Contain a carbonyl group

Naming Ketones Select the longest chain of carbon atoms containing the carbonyl group Number the chain from the end closest to the carbonyl group Determine the parent name from the number of C in the chain, replace the final -e with -one Name alkyl branches as usual

Functional Groups: Aldehydes Contain a carbonyl group H

Common Aldehydes

Naming Aldehydes Select the longest chain of carbon atoms containing the aldehyde group Number the chain calling the carbonyl C position 1 Determine the parent name from the number of C in the chain, replace the final -e with -al Name alkyl branches as usual

Carboxylic Acids Have carboxyl group, R1-COOH Always on end of chain Acid functional group –Weak acid

Functional Groups: Carboxylic acids

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Esters Replace acid H of carboxyl group with R group, R1-COO-R2 Sweet, fruity odors

Functional Groups: Esters Contain a carbonyl group

Naming Esters Select the longest chain of carbon atoms containing the ester group Name R2 as alkyl group Name R1 and carboxyl C like acid except change the –ic ending to -ate Put the pieces together, alkyl group first