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.
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.
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
cyclobutane
cyclopropane
2.
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.
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
+ HBr
B.
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.
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.
2.
Ethers
-oxygen singly bonded to two carbon atoms.
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 () bonded to at least one hydrogen atom. Add the suffix -al.
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.
+ O2
+ H2O
2-propanol +
oxygen
2-propanone acetone dimethyl ketone
+ water
General formula:
5.
Acids
contain a carboxyl group, ,general form, , suffix is an -ioc ending.
+ O2
+ H2O
ethanol +
oxygen
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.
+
+ H2O
acetic acid
+
methanol
methyl acetate**
+ water
**Note: the alcohol residue comes first, then the acid.
-Most esters have a very pleasant odor.
+
+ H2O
salicylic acid
+
methyl alcohol
methyl salicylate (wintergreen)
+ water
7.
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
are a NO2 group. Nitro- prefix.
E.
Nitrile
a carbon triple bonded to a nitrogen. Add -nitrile suffix.
III.
Miscellaneous
1.
Soaps
Animal and vegetable fats are esters made of
a.
Long-chain organic acids (fatty acids)
b.
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
+
3
fat
+ sodium hydroxide
glycerol
+
3 soap
Soap cleans because:
a.
Long chain hydrocarbon has a good solvent action on other hydrocarbons.
b.
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
+
+ H2O
salicylic acid
+
acetic acid
acetyl salicylic acid (aspirin)
+ water
3.
Acid Anhydrides
-a compound formed when two carboxyl groups join releasing a water.
) bonded to at least one hydrogen atom. Add the suffix -al.
O2
,general form, 
, suffix is an -ioc ending.
end has a high water solubility.
