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Honors Chemistry
Chapter 18 notes—Organic Chemistry
I. General
A. Organic chemistry—the study of carbon and its compounds
1. Carbon is unique among elements
a. it can bond to other carbon atoms to form chains as many as several thousand atoms long
b. it can bond to four other atoms at one time
c. its chains can have branches
d. it can form closed-ring structures
e. it can bond strongly to oxygen and nitrogen
f. it can form double and triple bonds
2. Carbon compounds are used all around us.
a. skin
b. plastic
c. gasoline
d. propane
e. dynamite
f. sugar
g. pyrethrins—natural insecticides
h. smells or flavors—vanilla
B. These compounds are vast and varied and they have their own rules
1. However, they can be classified into a relatively small number of groups that have similar
structures and properties
2. Prefixes that are used in organic chemistry
a. 1—methb. 2—ethc. 3—propd. 4—bute. 5—pentf. 6—hexg. 7—hepth. 8—octi. 9—nonj. 10—dec3. General structure groups
a. Aliphatic compounds—straight (chains) and cyclic (rings)
1) Hydrocarbons
a) Alkanes—single bonds
b) Alkenes—a double bond
c) Alkynes—a triple bond
2) Substituted hydrocarbons
a) Halides—halogens added
b) Alcohols—OH
c) Carboxylic Acids—COOH
d) Esters—R1COOR2
e) Ether—R1OR2
f) Ketone—CO
g) Aldehyde—CHO
h) Amines—RNH2
i) Amides—RCONH2
b. Aromatic compounds—delocalized electrons with a benzene ring
4. We will learn the IUPAC (International Union of Pure and Applied Chemistry) naming system for
most of these compounds.
II. Hydrocarbons
A. General
1. Defined—organic compound that consists of only carbon and hydrogen
2. Primary sources—natural gas, coal, and petroleum
B. Classes or groups
1. Alkanes—the simplest hydrocarbons (read p. 623-629)
a. General information
1) Can be in a chain or ring form
2) Straight chain—no branches
3) Branched chain—has branches
4) Ring—the chain bends and joins where it began
b. Simplified structures
1) In cyclic compounds the elements are left out and we use just the shapes—points
indicate carbons
2) The hydrogens can be left out in the structural formulas
3) An acceptable form also CH3 —CH2 —CH3
4) Also acceptable form CH3CH2CH3
c. Naming
1) Straight—the prefix and –ane
2) Branched—simplified version
a) find the longest continuous chain—this is the parent chain, name it like a straight
chain
b) number the parent chain carbons with the lowest possible numbers for the locants
(the branches)
c) change the branch names to a –yl form (methane to methyl)
d) list the locants in alphabetical order
e) separate numbers with commas and dashes for everything else
f) use the prefixes from normal naming system for identifying two or more identical
branches
g) Example: 4-ethyl-2,2-dimethyl octane
3) Cyclic compounds—add cyclo in front of the parent name (cyclopentane)
d. Isomers
1) Defined—compounds that have the same molecular formula but different structural
formulas
2) Isomer have the same molecular formulas, but different properties (they are totally
different compounds)
3) Example
a) butane
b) 2-methylpropane
4) the number of possible isomers increases rapidly as carbons are added to the parent
chain—butane only has 2 isomers, pentane has 3 isomers, hexane has 5 isomers, and
more than 4 billion isomers for C30H62
e. properties
1) the more carbons in the straight chain the higher the melting and boiling points
a) 1-4 carbons are gases at room temperature
b) 5-16 carbons are liquids at room temperature
c) more than 16 carbons are solids at room temperature
2) alkanes are relatively unreactive
3) alkanes are non-polar because of the carbon-carbon and carbon-hydrogen bonds
4) dissolve only in organic solvents (non-polar)
5) known as saturated hydrocarbons because they have as many Hydrogen atoms as is
possible
2. Alkenes—read p. 629-631
a. General information
1) hydrocarbons with a double bond
2) unsaturated hydrocarbons because they don’t have all the hydrogens that they could
possibly have
3) ethene is the simplest alkene and is used in conversion to plastic and is used in ethylene
glycol (antifreeze), it is also used to ripen fruits
b. Naming alkenes
1) named similarly to alkanes although we change the suffix to –ene
2) if there are four or more carbons then a number preceding the parent chain name is
needed to indicate the location of the double bond.
3) for numbering the carbons, number them so that the double bond gets the lowest
number possible
4) Example: 1-butene or 2-butene or 2-pentene
c. Positional isomers
1) When the double bond is at a different location, then the structural formula and the
properties are different. These are positional isomers.
2) Because the double bond does not allow the carbons in the bond to rotate, then the
placement of the branches can create isomers—these are geometric isomers
3) Geometric isomer names (see page 6310
a) cis- if on the same side
b) trans- if on opposite sides
d. Reactivity of alkenes
1) more reactive than alkanes, because the extra electrons in the double bond are not held
as tightly
2) alkenes readily undergo synthesis reactions
3) hydrogenation is a synthesis reaction that puts the hydrogens back into the double bond,
making the alkene to become an alkane
3. Alkynes (read p. 633)
a. General information
1) hydrocarbons with a triple bond
2) unsaturated hydrocarbon
3) ethyne (acetylene) is the most important commercial alkyne
a) used in vinyl and acrylic materials
b) also used in oxyacetylene torches for welding and cutting metal
b. Naming alkynes
1) similar to alkenes, but with the suffix –yne
2) make sure that the triple bond gets the lowest number possible
c. Properties
1) Very reactive, so most don’t exist and if they do, it isn’t for long
2) They can be synthesized from other organic compounds
3) Melting and boiling points increase with increasing chain lengths
4) Similar properties to Alkenes
5) melting and boiling points are higher than alkanes
6) they undergo synthesis reactions, it is normally done stepwise to an alkene and then to
an alkane
C. Aromatic Hydrocarbons (read page 636)
1. Structure
a. Originally Kekule described it as a six-carbon ring with alternating single and double bonds
b. Now it is assumed that the “extra” electrons are shared by all six carbons in a “cloud”—
delocalized electrons
c. because of this arrangement, aromatics do not behave like alkenes, they are quite stable
d. the simplest compound is benzene (C6H6)
e. all aromatics have benzene as a base
f. diagram is shown on page 636
2. Name
a. originally named because most have distinctive aromas
b. examples: vanilla, naphthalene (p-dichloro-benzene, mothballs)
3. When a branched group, they are known as aryl- groups
D. Sources of Organic Compounds (Read pages 636-639)
1. Natural gas
a. Deposits contain large amounts of methane, along with smaller amounts of alkanes up to
about 5 carbons in length.
b. It also contains the inorganic gases of CO2, N2, and helium
c. Formed the same way as petroleum; therefore, frequently found in petroleum deposits
d. Easily passes through pipes therefore is used as a fuel
e. Also used a raw material for synthesis of small organic compounds
2. Petroleum
a. General info
1)Complex mixture, mostly of alkanes and cyclic alkanes
2) formed from decaying organic material under high temperature and pressure
conditions—normally involves water
3) Products: gasoline, jet fuel, kerosene, diesel fuel, fuel oil, asphalt, and oil
b. Fractional distillation
1) a physical property that allows hydrocarbons to be separated is their different boiling
points
2) Crude oil is heated and then the various hydrocarbons are removed at varying levels,
based on their varied boiling points (see p. 638)
c. Cracking and reforming
1) The use of catalysts and/or high temperatures to break down large hydrocarbons into
smaller hydrocarbons.
2) reforming is the basically the same thing but is used to form aromatic hydrocarbons
3. Coal
a. a fossil fuel like natural gas and petroleum
b. the most abundant fossil fuel
c. formed from the remains of plants that became buried underwater and subjected to high
pressures
d. Composed primarily of carbon, but has some mineral impurities
e. Used mainly as a fuel.
f. obtained from surface or underground mines
1) surface mines damage the environment and must be restored
2) underground mines are dangerous
III. Substituted Hydrocarbons (read pages 640-644)
A. Functional Groups
1. A hydrogen of a hydrocarbon can be substituted with a functional group; hence, making a
substituted hydrocarbon
2. A functional group is largely responsible for the chemical behavior of the parent molecule
3. Functional groups can be atoms, groups of atoms, or bond arrangements
4. R is traditionally used to represent the parent molecule (the alkyl group) in generic formulas
B. The Groups
1. Halides
a. General formula R—X
b. a halogen is the functional group
c. properties: high density
d. uses: refrigerants, solvents, pesticides, moth repellants, some plastics
e. biological functions: thyroid hormones
f. examples: chloroform, dichloromethane, thyroxin, chlorofluorocarbon refrigerant, DDT,
PCBs, PVC
g. naming
1) ending stays the same
2) add the halogen prefix before the parent molecule
3) use prefixes if more than one
4) use numbers if necessary
5) 1,2 -- dichloroethene
2. Alcohols
a. General formula R-OH
b. a hydroxyl group (–OH) is the functional group, it has at least one
c. properties: polar, high boiling points
d. uses: disinfectant, mouthwash, hair spray ingredient, antifreeze
e. biological functions: reactive groups in carbohydrates, product of fermentation
f. examples: methanol, ethanol, cholesterol
g. naming
1) ending is changed to –ol
2) use a number in front of the parent compound if necessary to identify the hydroxyl group
location
3. Ketones and Aldehydes
O
O
“
“
a. General formula is R—C—R’ for ketones and R—C—H for aldehydes
b. a carbonyl group (–CO) is the functional group
c. properties: very reactive, distinctive odors
d. uses: solvents, flavorings, embalming agent, manufacture of plastics and adhesives
e. examples: acetone, formaldehyde, cinnamon, vanilla, and almond flavorings
f. naming
1) Ketones
4.
5.
6.
7.
a) ending is changed to –one
b) if a number is needed it is placed in front of the –one
c) pentan—3—one
2) Aldehydes
a) ending is changed to –al
b) propanal
Carboxylic Acids
O
“
a. General formula is R—C—OH
b. a carboxyl group (–COOH) is the functional group
c. properties: acidic, usually water-soluble, strong unpleasant odors, form metal salts in acidbase reactions
d. uses: vinegar, tart flavoring, skin-care products, production of soaps and detergents
e. biological functions: pheromones, ant-sting (actually a bite) toxin, causes rancid-butter and
smelly feet odors
f. examples: acetic acid (in vinegar), formic acid, citric acid, salicylic acid
g. naming
1) ending is changed to –oic acid
2) butanoic acid
Ether
a. General formula is R—O—R
b. an Oxygen stuck in the middle of two hydrocarbon groups is the functional group
c. properties: mostly unreactive, insoluble in water, volatile
d. uses: anesthetics, solvents for fats and waxes
e. examples: diethyl ether
f. naming
1) ending is changed to ether
2) name the alkyl groups on either side with the smaller one first
3) methyl ethyl ether
Esters
O
“
a. General formula is R—C—O—R’
b. derived from carboxylic acids in which the –OH has been replaced with an –OR from an
alcohol
c. properties: strong aromas, volatile
d. uses: artificial flavorings and fragrances, polyester fabric
e. biological functions: fat storage in cells, DNA phosphate-sugar backbone, natural flavors and
fragrances, beeswax
f. examples: banana oil, oil of wintergreen, triglycerides (fats)
g. naming
1) the R’ group is named by its alky name in front
2) the carboxylic acid is named with its ending changed to –oate
3) octyl ethanoate—orange flavor or odor
Amines
a. General formula is R—NH2
b. ammonia is the parent compound NH3
c. properties: basic, ammonia-like odor
d. uses: solvents, synthetic peptide hormones, fertilizer, dyes
e. biological functions: in amino acids, peptide hormones, proteins, distinctive odor of some
cheeses
f. examples: urea, putrescine, cadaverine, aspartame
g. naming
1) ending is amine
2) all alky groups are named, smallest first
3) methylethylpropylamine
8. Amides
O
“
a. General formula is R—C—NH2
b. an amine takes the place of an –OH group in a carboxylic acid
c. properties: neutral, most are solids
d. naming
1) ending becomes amide
2) propanamide
C. Sources of Functional Groups
1. Alkanes are not very reactive, so it is difficult to synthesize functional groups from alkanes
2. Alcohols are much easier to convert and are the industry standard
3. Ethene is produced from the cracking of petroleum, this is easily converted into ethanol when
reacted with water
4. A second source is natural ethanol.
a. obtained when yeast cells ferment sugars and starches found in plant materials
b. grapes are a primary source for this
c. does not produce the quantities of ethanol like the reaction of ethene with water
d. used in industry mainly to produce the ethanol in alcoholic beverages
IV. Plastics and other polymers
A. Introduction
1. Polymer—a large molecule (hundreds or thousands of units) that is made up of many smaller,
repeating units
2. Monomer—the smaller individual units in a polymer
3. Polyethylene plastic is a polymer of gaseous ethylene
4. Obviously the properties of the polymer are different than the monomer’s properties
B. Synthetic polymers
1. a polymer that is man-made
2. this has been occurring for only about 100 years
3. nylon raincoats, plastic wrap, sandwich bags, plastic containers, light-weight fabrics, football
pads, Styrofoam cups, etc
4. many polymers have added convenience to our lives
C. Natural polymers
1. polymers produced by living cells or organisms
2. proteins, DNA, chitin exoskeletons of insects, wool, spiderwebs, cocoons, jelly-like substance
that surrounds amphibian eggs, cellulose fibers
3. many synthetic polymers are man’s attempts to reproduce or simulate a natural polymer
D. Structure of polymers
1. repeating pattern of monomers
2. any piece representing a polymer must include at least one complete repeating unit
3. comparison between starch and cellulose
a. cellulose the O bond is upward
b. starch the O bond is downward
c. this “minor” change changes “everything”
E. Polymerization
1. Definition—the process of linking monomers to form a polymer
2. Addition reactions
a. the double bonds are broken and replaced with single bonds
b. all atoms that one originally had are still there
3. Condensation reactions
a. they add similarly to addition reactions; however, a water molecule is given off
b. frequently it is an –OH from a carboxyl group and a –H from an amino group
4. Cross-linking
a. Used in conjunction with addition and condensation reactions
b. It links different chains of the polymer together making it stronger
c. Goodyear discovered this with rubber and sulfur
1) process is known as vulcanization
2) named after the Roman god of fire and metalworking
F. Plastics
1. The terms plastic and polymer are frequently used synonymously, but not all polymers are
plastics
2. Plastics are polymers that can be molded into different shapes
3. Thermoplastic—ability of a plastic to soften and harden repeatedly when heated and cooled
a. easily recycled because it can be heated and remolded
b. polyethylene and polyvinyl chloride are examples
4. Thermosetting—plastics that harden permanently when molded
a. usually are rigid because of many cross-links
b. will not soften enough to be remolded
c. resin bakeware is an example