Chapter 12 Organic and Biological Chemistry

Organic Chemistry The chemistry of carbon compounds. Carbon has the ability to form long chains. Without this property, large biomolecules such as proteins, lipids, carbohydrates, and nucleic acids could not form.

Hydrocarbons Four basic types:  Alkanes  Alkenes  Alkynes  Aromatic hydrocarbons

Alkanes Only single bonds. Saturated hydrocarbons.  “Saturated” with hydrogens.

Formulas Lewis structures of alkanes look like this. Also called structural formulas. Often not convenient, though…

Formulas …so more often condensed formulas are used.

Properties of Alkanes 2(# of C) + 2 = # of H Only van der Waals force: London force. Boiling point increases with length of chain.

Isomers Have same molecular formulas, but atoms are bonded in different order.

Organic Nomenclature Three parts to a compound name:  Base: Tells how many carbons are in the longest continuous chain.

Organic Nomenclature Three parts to a compound name:  Base: Tells how many carbons are in the longest continuous chain.  Suffix: Tells what type of compound it is.

Organic Nomenclature Three parts to a compound name:  Base: Tells how many carbons are in the longest continuous chain.  Suffix: Tells what type of compound it is.  Prefix: Tells what groups are attached to chain.

To Name a Compound… 1.Find the longest chain in the molecule. 2.Number the chain from the end nearest the first substituent encountered. 3.List the substituents as a prefix along with the number(s) of the carbon(s) to which they are attached.

To Name a Compound… If there is more than one type of substituent in the molecule, list them alphabetically.

Cycloalkanes Carbon can also form ringed structures. Five- and six-membered rings are most stable.  Can take on conformation in which angles are very close to tetrahedral angle.  Smaller rings are quite strained.

Reactions of Alkanes Combustion Substitution Dehydrogenation

Combustion 2C 4 H O > 8CO H 2 O At high temperatures alkanes react vigorously with oxygen.

Substitution CH 4 + Cl 2  CH 3 Cl + HCl One or more of the hydrogen atoms of the alkane are replaced by different atoms.

Dehydrogenation CH 3 CH 3  CH 2 =CH 2 + H 2 Hydrogen atoms are removed and the product is an unsaturated hydrocarbon

Alkenes Contain at least one carbon–carbon double bond. Unsaturated.  Have fewer than maximum number of hydrogens.

Structure of Alkenes This creates geometric isomers, which differ from each other in the spatial arrangement of groups about the double bond.

Nomenclature of Alkenes Chain numbered so double bond gets smallest possible number. cis- alkenes have carbons in chain on same side of molecule. trans- alkenes have carbons in chain on opposite side of molecule.

Addition Reactions Hydrogenation Halogenation Polymerization

Hydrogenation CH 2 =CH 2 + H 2  CH 3 CH 3 The addition of a hydrogen atom to each carbon formerly involved in the double bond.

Halogenation CH 2 =CHCH 2 CH 2 CH 3 + Br 2  CH 2 BrCHBrCH 2 CH 2 CH 3 Adding halogens to unsaturated hydrocarbons.

Polymerization Many small molecules (monomers) are joined together to form a large molecule (polymer) A dimer is two monomers joined together Process used to make synthetic fibers, rubbers and plastics nCH 2 = CH 2  -(CH 2 -CH 2 )- Where n represents a large number(usually several thousand)

Polymers Copolymers are two different monomers joined together Homopolymers are two of the same monomers joined together Common polymers- vinyl (siding), polyester, nylon, polyethylene (plastic), polystyrene (styrofoam)

Polymers Undergo Various Reactions  Addition reactions Monomers simply add together…no side product  Condensation reactions A small molecule, such as water, is produced for each extension of the polymer chain

Alkynes Contain at least one carbon–carbon triple bond. Carbons in triple bond have linear geometry. Also unsaturated.

Nomenclature of Alkynes Analogous to naming of alkenes. Suffix is -yne rather than –ene. 4-methyl-2-pentyne

Aromatic Hydrocarbons Cyclic hydrocarbons. Molecule is planar. Many aromatic hydrocarbons are known by their common names.

Structure of Aromatic Compounds Two substituents on a benzene ring could have three possible relationships  ortho-: On adjacent carbons.  meta-: One carbon between them.  para-: On opposite sides of ring.

Functional Groups Term used to refer to parts of organic molecules where reactions tend to occur.

Alcohols Contain one or more hydroxyl groups, —OH Named from parent hydrocarbon; suffix changed to -ol and number designates carbon to which hydroxyl is attached. Naming: _____ol

Ethers Tend to be quite unreactive. Therefore, they are good polar solvents.

Carbonyl Compounds Contain C—O double bond. Include many classes of compounds.

Aldehydes At least one hydrogen attached to carbonyl carbon. Aldehydes typically have strong odors Common examples: 1. vanillin propanal 2. cinnamaldehyde Naming: _____al

Ketones Two carbons bonded to carbonyl carbon. Naming: _____one Acetone is a common example 3-pentanone

Carboxylic Acids Have hydroxyl group bonded to carbonyl group. Tart tasting. Pungent odors. Carboxylic acids are weak acids. Naming: _____oic acid Can be written as: CH 3 COOH ethanoic acid or vinegar

Carboxylic Acids

Esters Products of reaction between carboxylic acids and alcohols. Found in many fruits and perfumes. butanoate

Amines Organic bases. Generally have strong, unpleasant odors.

Amides Formed by reaction of carboxylic acids with amines. This is the reaction that occurs between amino acids

Amino Acids and Proteins A condensation reaction between the amine end of one amino acid and the acid end of another produces a peptide bond.