Chapter 22 - Organic and Biological Molecules

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

**** 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

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

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

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

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