22.1 Alkanes: Saturated Hydrocarbons

• They are compounds composed of mostly carbon and hydrogen atoms that typically contain chains or rings of carbon atoms

• Alkanes:

  • It contains compounds with only C¬C single bonds

  • They are said to be saturated because each carbon present is bonded to the maximum number of atoms (4)

  • The carbon atoms are described as being sp3 hybridized

  • Their structural isomerism involves the formation of branched chains

  • They react with O2 to form CO2 and H2O (called a combustion reaction)

  • They undergo substitution reactions

• Alkenes:

  • It contains one or more C“C double bond

  • The simplest alkene is C2H4 (ethylene) which is described as containing sp2 hybridized carbon atoms

  • Restricted rotation about the C“C bonds in alkenes can lead to cis-trans Isomerism

  • They undergo additional reactions

• Alkynes:

  • It contains one or more C‚C triple bonds

  • The simplest example is C2H2 (acetylene), described as containing sp-hybridized carbon atoms

  • They also undergo additional reactions

• Aromatic hydrocarbons

  • It contains rings of carbon atoms with delocalized p electrons

  • It undergoes substitution reactions rather than addition reactions

22.2 Alkenes and Alkynes

• **** Multiple carbon-carbon bonds result when hydrogen atoms are removed from alkanes

• The root hydrocarbon name ends in -one rather than -ane

• In alkenes containing more than three carbon atoms, the location of the double bond is indicated by the lowest numbered carbon atom involved in the bond

  • Alkynes are unsaturated hydrocarbons containing at least one triple carbon-carbon bond

  • The simplest alkyne is C2H2

  • For cyclic alkenes, number through the double bond toward the substituent

• Since alkenes and alkynes are unsaturated, their most important reactions are addition reaction

• Halogenation of unsaturated hydrocarbons involves the addition of halogen atoms

• Another important reaction involving certain unsaturated hydrocarbons is polymerization, a process in which many small molecules are joined together to form a large molecule

22.3 Aromatic Hydrocarbons

• They contain carbon, hydrogen, and oxygen

• It serves as a food source for most organisms

• Monosaccharides are most commonly five-carbon and six-carbon polyhydroxy ketones and aldehydesMonosaccharides combine to form more complex carbohydrates, such as sucrose, starch, and cellulose

• Benzene is the simplest aromatic molecule. More complex aromatic systems can be viewed as consisting of a number of “fused” benzene rings

• When benzene is used as a substituent, it is called the phenyl group

22.4 Hydrocarbon Derivatives

• They are molecules that are fundamentally hydrocarbons but that have additional atoms or groups of atoms

• Alcohols are characterized by the presence of the hydroxyl group

  • Alcohols are classified according to the number of hydrocarbon fragments bonded to the carbon where the OOH group is attached

  • They usually have much higher boiling points than might be expected from their molar masses.

  • Although there are many important alcohols, the simplest ones, methanol, and ethanol, have the greatest commercial value.

• Methanol is prepared industrially (approximately 4 million tons annually in the United States) by the hydrogenation of carbon monoxide:

• Methanol is used as a starting material for the synthesis of acetic acid and for many types of adhesives, fibers, and plastics

• Ethanol is the alcohol found in beverages such as beer, wine, and whiskey;

• It is produced by the fermentation of glucose in corn, barley, grapes, etc

• Many carboxylic acids are synthesized by oxidizing primary alcohols with a strong oxidizing agent

22.5 Polymers

• Polymers form the basis for synthetic fibers, rubbers, and plastics and have played a leading role in the revolution that has been brought about in daily life by chemistry

• The first synthetic polymers were produced as by-products of various organic reactions and were regarded as unwanted contaminants

• Polyethylene is a tough, flexible plastic used for piping, bottles, electrical insulation, packaging films, garbage bags, and many other purposes.

  • Its properties can be varied by using substituted ethylene monomers.

• Other polyethylene-type polymers are made from monomers containing chloro, methyl, cyano, and phenyl substituents,

• Large molecules formed from many small molecules (called monomers)

• Addition polymerization: Monomers add together by a free radical mechanism

• Condensation polymerization: Monomers connect by splitting out a small molecule, such as water

• Molecular weight (not molar mass) is the common terminology in the polymer industry

22.6 Natural Polymers

• A class of natural polymers with molar masses ranging from 600 to 1,000,000

• Fibrous proteins form the structural basis of muscle, hair, and cartilage

• Globular proteins perform many biologic functions, including transport and storage of oxygen, catalysis of biologic reactions, and regulation of biological systems

• The protein is built in several steps. First, a tRNA molecule brings an amino acid to the mRNA

  • Once this amino acid is in place, another tRNA moves to the second codon site of the mRNA with its specific amino acid

  • The process is repeated down the chain, always matching the tRNA anticodon with the mRNA codon

• Building blocks of proteins (monomers) are amino acids, which connect by a condensation reaction to form a peptide linkage

• Hydrogen bonding can also occur between different protein chains, joining them together in an arrangement called a pleated sheet

• The overall shape of the protein is called its tertiary structure and is maintained by several different types of interactions: hydrogen bonding, dipole-dipole interactions, ionic bonds, covalent bonds, and London dispersion force

• Protein structure:

  • Primary: The order of amino acids in the chain

  • Secondary: The arrangement of the protein chain

  • Tertiary structure: The overall shape of the protein

• Carbohydrates from another class of biologically important molecule