Download Erik`s Chemistry: Organic Chemistry Notes - ECHS Chemistry

Organic Chemistry
Notes
AP
Chemistry
(Chapter 22
)
Back To Erik's Chemistry: Main Page
All organic chemistry is based upon unique properties of the carbon atom.
Carbon, C, hybridization to 3 sp3 orbitals, carbon can now form 4 bonds, may be
single, or in combination of double (sp2) or triple bonds (sp). Carbon forms very
strong bonds with many non-metal atoms, H, O, Cl, N.
Note: silicon and germanium are in the same family and form 4 bonds, but the
bond energy is low, so weak bonds are formed. This severely restricts their
chemistry.
I.
Hydrocarbons
4 categories: alkanes, alkenes, alkynes, and aromatic compounds
1.
Alkanes: carbon atoms are bonded to each other with single bonds. Each C has
4 bonds (sp3 hybrid). Bonds are directed to corners of a tetrahedron
(bond angles of 109.5o). Chains are "zig-zag". The general rule for
writing formulas is 2n+2. Where n represents the number of carbons
and 2n+2 equals the number of hydrogens.
methane (1C), ethane (2C's), propane (3C's), butane (4C's), pentane (5C's), hexane
(6C's), heptane (7C's), octane (8C's), nonane(9C's), decane(10C's)
Isomerization- same molecular formula, but different structure. Also creates
different properties for the molecule. The number of possible isomers
increases rapidly as the length of the chain increases.
n-butane
2-methyl propane (iso-butane)
**When adding carbon "groups" to the main chain, add the ending yl. e.g. methyl, ethyl,
propyl, butyl. These are called substituents.
n-hexane
2n+2
2(6)+2=14
Therefore it is
C6H14
2-methyl pentane
3-methyl pentane
2,3-dimethylbutane
2,2-dimethyl butane (not 3,3-dimethyl
butane)
Alkanes, straight or branched chains, all have an exterior which is mostly hydrogen
atoms. Surface of one molecule is quite like any other. No well-defined + or - center, so
they are non-polar. Soluble in each other and in other non-polar solvents. (not soluble in
water, which is very polar).
Alkanes are rather unreactive chemically. Principle reaction is burning in air (combustion
reaction). Also are involved in substitution reactions.
Cycloalkanes: molecular formula has 2 less H atoms than straight chain (2n).
cyclohexane
2.
cyclobutane
cyclopropane
Alkenes (unsaturated hydrocarbon, olefin) contains one double bond. Made by
cracking an alkane (heating long-chain alkane in presence of catalyst).
This causes (among other things) a double bond to form, and the
elimination of two H's. General rule: 2n, creates at least one pi bond.
Has sp2 hybridization on the double bond.
No rotation about the double bond, this leads to the formation of geometric isomers.
cis-2-butene
trans-2-butene
The presence of the double bond makes alkenes more reactive than alkanes. Also can
polymerize.
3.
Alkynes contain 1 triple bond. General rule, 2n-2, sp hybridization around the
triple bond.
acetylene
1-butyne
ethyne
The presence of the triple bond makes these very reactive.
4.
Aromatic
hydrocarbons-all involve the molecule benzene C6H6.
Aromatic compounds are very stable. The double bonds in benzene are delocalized
(creates resonance). Benzene molecules are very carcinogenic.
ortho-dichloro
benzene
meta-dichloro
benzene
para-dichloro
benzene
note: each benzene still has H's at each C
without a chlorine
5.
Types of Reactions of Alkanes and Alkenes
A. Substitution: characteristic of single bonds (alkanes).
+ Br2
B.
+ HBr
Addition: characteristic of double bond (alkenes).
+ Br2
Note: no byproduct.
Addition reactions are a good test for a double bond. A diatomic bromine solution of
carbon tetrachloride is reacted with the suspected compound. If a double bond is
present, red color (from Br2) will quickly fade.
II. Hydrocarbon Derivatives
1.
Alcohols contain the hydroxide group, OH, substituted for hydrogen. Suffix is
-ol.
methyl alcohol
ethyl alcohol
propyl alcohol
isopropyl alcohol
methanol
ethanol
propanol
2-propanol
General formula R-OH, where R is an alkyl group. Hydrogen bonding in the -OH group
causes alcohols to have a high boiling point.
a.
Can be formed by oxidation (addition of oxygen, removal of H on both).
+O2
Oxidizing a hydrocarbon gives an alcohol.
b.
Can be formed by reduction (addition of hydrogen, removal of oxygen, or both)
+H2
This process is used for about 80% of industrial ethanol production.
Methanol-present in liquid distillate from heating wood and oxygen, "wood alcohol",
deadly and causes blinding.
-oxygen singly bonded to two carbon atoms.
2. Ethers
dimethyl ether
ethyl methyl ether
diethyl ether (anesthetic)
General formula R-O-R'
Diethyl ether-anesthetic, good solvent. Vapors highly flammable.
3.
Aldehydes have carbonyl group (
atom. Add the suffix -al.
) bonded to at least one hydrogen
formaldehyde
acetaldehyde
propionaldehyde
methanal
ethanal
propanal
General formula:
The boiling point for aldehydes is lower than the corresponding alcohol's, since there is
no hydrogen bonding. The boiling point is much higher than corresponding saturated
hydrocarbons, since
bond is highly polar.
Produced by oxidizing an alcohol with a terminal -OH group. Reduction is the oppsite
process.
4.
Ketones have a carbonyl on the interior of the chain. Oxidation of an alcohol
with non-terminal -OH. Suffix is an -one ending.
+ H2O
+ O2
2-propanol +
General formula:
oxygen
2-propanone
acetone
dimethyl ketone
+ water
5.
Acids
contain a carboxyl group,
an -ioc ending.
,general form,
+ O2
ethanol +
oxygen
, suffix is
+ H2O
acetic acid
(vinegar)
+ water
formic acid
propionic acid
butyric acid
from "formica" (ants)
acetic acid
(rancid butter)
methanoic acid
ethanoic acid
propanioc acid
Organic acids ionize by:
+ H+
-Most are weak acids.
-As the length of the chain increases, organic acids become less soluble in water and
more soluble in non-polar solvents (remember that the -OH creates high polarity).
6.
Esters
are produced by a reaction between an acid and an alcohol.
+
acetic acid
+
+ H2O
methanol
methyl acetate**
+ water
**Note: the alcohol residue comes first, then the acid.
-Most esters have a very pleasant odor.
+
salicylic acid
7.
+
+ H2O
methyl alcohol
methyl salicylate
(wintergreen)
+ water
Nitrogen Functional Groups
A. Amines are derivatives of ammonia in which one or more N-H bonds have
been replaced with a N-C bond. The name amine represents the NH2 functional group.
Primary amine
Secondary amine
Tertiary amine
B. Amides have a carbonyl group and an amine (pronounced a-mids). Add amide suffix.
C. Amino Acids are organic acids with a amine group directly next to the
carboxyl group.
D. Nitro
E. Nitrile
III. Miscellaneous
are a NO2 group. Nitro- prefix.
a carbon triple bonded to a nitrogen. Add -nitrile suffix.
1.
Soaps
Animal and vegetable fats are esters made of
a.
b.
Long-chain organic acids (fatty acids)
Various alcohols, glycerol (glycerin) is the most common. Glycerol is a
triol.
Reacting a fat with NaOH splits the fat into glycerin and the sodium salt of the fatty acid.
This sodium salt is the soap.
+ 3 NaOH
fat
+ sodium hydroxide
+
glycerol
3
+
3 soap
Soap cleans because:
a.
b.
Long chain hydrocarbon has a good solvent action on other hydrocarbons.
end has a high water solubility.
Soaps from 'scum" in hard water. "Scum" is a precipitates of the Ca2+ and Mg2+ of the
soap. Detergents contain poly phosphorus ions, which tie up the Ca2+ and Mg2+ ions so
the detergent can do its work.
2.
Aspirin
+
salicylic acid
+
+ H2O
acetic acid
acetyl salicylic acid
(aspirin)
+ water
3.
Acid Anhydrides -a compound formed when two carboxyl groups join
releasing a water.
+
H2O +
back to top
Back To Erik's Chemistry: Main Page
Any comments will be appreciated. Please e-mail me at [email protected]
URL: http://members.tripod.com/~EppE/organic.htm
This page was made by Erik Epp.