Download Unit X Organic Chem (SmartBoard)

Organic Chemistry
A.
Introduction
1.
Organic chemistry is defined as the chemistry of CARBON
compounds. There are a huge number of organic compounds.
This results from the fact that carbon forms chains involving
several carbon atoms linked to each other in a straight-line fashion,
in a “circular” pattern, or in a branched pattern. In addition, the
carbon atoms may form single, double, or triple bonds to
neighbouring atoms.
2.
Organic compounds are found in petroleum, natural gas, and all
living things. The largest industry involving organic chemistry is
the manufacture of petrochemicals. Petroleum is the starting
material for a vast range of products. Petroleum is separated
(“fractioned”) and refined for use in gasoline and oil, while other
“fractions” of petroleum are chemically altered to serve as raw
materials for a huge array of industrial processes such as the
manufacture of plastics, solvents, pharmaceuticals, and personal
care products.
UNIT X — ORGANIC CHEMISTRY
2
B.
Alkanes
1.
A carbon atom can form bonds to four other atoms (carbon has a
valence of four).
A HYDROCARBON is a compound containing only hydrogen
and carbon.
There are many ways to represent a hydrocarbon formula,
depending on how compact one wants to write the formula.
EXAMPLE X.1 REPRESENTING HYDROCARBONS
Problem: Write the structure of propane, C3H8 as full structure,
condensed structure, molecular formula, and carbon
skeleton.
Solution:
Full Structure
H H H
| |
|
H—C—C—C—H
| |
|
H H H
Condensed structure
CH3—CH2—CH3
Molecular formula
C3H8
Carbon skeleton
C—C—C
UNIT X — ORGANIC CHEMISTRY
2.
3
ALKANES (A HOMOLOGOUS SERIES)
methane = CH4
H
|
H—C—H
|
H
propane = C3H8
H H H
| |
|
H—C—C—C—H
| |
|
H H H
ethane = C2H6
butane = C4H10
H H
| |
H—C—C—H
| |
H H
H H H H
| |
| |
H—C—C—C—C—H
| |
| |
H H H H
Notice that each carbon forms four bonds. The number of H’s
attached is 4 minus the numbers of C’s attached.
methane 1 CH4
ethane
2 C2H6
CH3—CH3
propane
3 C3H8
CH3—CH2—CH3
butane
4 C4H10
CH3—CH2—CH2—CH3
pentane
5 C5H12
CH3—CH2—CH2—CH2—CH3
hexane
6 C6H14
CH3—CH2—CH2—CH2—CH2—CH3
heptane
7 C7H16
CH3—CH2—CH2—CH2—CH2—CH2—CH3
octane
8 C8H18
CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH3
nonane
9 C9H20
CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH3
decane
10 C10H22
CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—
CH2—CH3
An ALKANE is a hydrocarbon in which all the carbon atoms are
connected by single bonds.
UNIT X — ORGANIC CHEMISTRY
2.
4
Each of the molecules differs by the number of carbon atoms
linked to one another to form a “CARBON CHAIN”. A series of
structures that differ from each other by one structural unit, in this
case —CH2—, are called a HOMOLOGOUS SERIES.
Because the chain of carbon atoms extends in a straight-line they
are called “STRAIGHT-CHAIN” or “UNBRANCHED”
hydrocarbons.
The names of the all the above hydrocarbons end in “ANE”
because they are “ALKANES”. Alkanes are said to be
“SATURATED” hydrocarbons because each carbon atom is
bonded to the maximum possible number of other atoms.
Each of the single bonds between carbon atoms is able to rotate
freely, leading to a highly flexible chain which can take many
shapes.
The following molecules all represent heptane, C7H16
CH3—CH2
CH2—CH3
|
|
CH2—CH2—CH2
CH3—CH—CH3
|
CH2—CH2—CH2—CH3
CH3—CH2—CH2—CH2—CH2—CH0—CH3
Assign #1
3.
A hydrocarbon can also have “SIDE BRANCHES” which are
also hydrocarbon chains. The attached groups are called “ALKYL
GROUPS”.
CH3—CH—CH2—CH2—CH2—CH3
|
CH2—CH3
An ALKYL GROUP is an alkane, which has lost one hydrogen
atom.
UNIT X — ORGANIC CHEMISTRY
5
An alkyl group is named by changing the “ANE” ending of the
original hydrocarbon to “YL”.
ORIGINAL HYDROCARBON
4.
ALKYL GROUP
methane = CH4
methyl = CH3—
ethane = CH3—CH3
ethyl = CH3—CH2—
propane = CH3—CH2—CH3
propyl = CH3—CH2—CH2—
butane = CH3—CH2—CH2—CH3
butyl = CH3—CH2—CH2—CH2—
When an alkyl group is attached to another hydrocarbon, the
resulting molecule is called a SUBSTITUTED
HYDROCARBON or a BRANCHED HYDROCARBON.
NAMING A SUBSTITUTED HYDROCARBON:
i)
First find the longest continuous chain of carbon atoms. This
longest chain is called the PARENT hydrocarbon. (Look at
branch points.)
C—C—C—C—C—C—C—C
|
C—C—C—C
9 Carbons
C—C—C—C
C—C—C
|
|
C—C—C—C—C—C—C
|
C—C
10 carbons
Assign 2ace
ii) Write the CARBON NUMBER at which the alkyl group is
attached followed by a dash “—“.
iii)
Name the alkyl group.
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iv)
Name the longest or parent hydrocarbon to which the alkyl
group is attached. (The carbon atoms in the parent
hydrocarbon are numbered consecutively from the end of
the hydrocarbon which gives the lowest possible set of
numbers (address) to the attached groups.
Assign 3-6ace
v) If more than one different alkyl group is attached to the
hydrocarbon, then list the alkyl groups
ALPHABETICALLY preceded by its number and a dash.
vi)
If an alkyl group is repeated, list each carbon number where
the repeated group is attached, separated by commas and the
prefix di, tri, tetra, etc. to show how many identical groups
are attached.
EXAMPLE X.2 NAMING SUBSTITUTED HYDROCARBONS
Problem: Name the following substituted hydrocarbons.
Solution:
C—C—C—C—C—C—C—C
|
C—C
3–ethyloctane
C—C—C—C—C—C—C
|
|
C
C—C
3–ethyl–5–methylheptane
C
|
C—C—C—C—C—C—C—C—C
|
|
|
C—C C
C
Assign 7-9 ace
3–ethyl–4,4,6–trimethylnonane
UNIT X — ORGANIC CHEMISTRY
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C.
Structural Isomers
1.
It is possible for two or more molecules to have the same
molecular formula (same number and types of atoms) but
different arrangement of atoms (structure).
All of the following molecules have the molecular formula C5H12.
CH3—CH2—CH2—CH2—CH3
Pentane
CH3—CH—CH2—CH3
|
CH3
2–methyl butane
CH3
|
CH3—C—CH3
|
CH3
dimethyl propane
STRUCTURAL ISOMERS are compounds which have the same
molecular formula but a different arrangement of atoms.
Assign 11-13
2.
Hydrocarbons which connect in a head–to–tail “CIRCLE” are
called CYCLIC HYDROCARBONS or CYCLOALKANES.
H2C—CH2
\ /
CH2
H2C — CH2
|
|
H2C — CH2
cyclopropane
cyclobutane
Assign 14
cyclopentane
cyclohexane
UNIT X — ORGANIC CHEMISTRY
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NAMING CYCLOALKANES:
i)
follow the same rules as straight–chain alkanes, except that a
single substituent does not use a number to indicate the
position of attachment.
ii)
If there is more than one substituent, the first substituent is
assumed to be at the “1” position and the remaining
substituents are numbered either clockwise or
anticlockwise to have the lowest set of overall values.
EXAMPLE X.3 NAMING CYCLOALKANES
Problem: Name the following cycloalkanes.
Solution:
—C
methyl cyclopentane
C—C
/
C—
—C
2–ethyl-1,4–dimethyl cyclohexane
Ignore di, tri… when writing the order
Assign 15-16ace
UNIT X — ORGANIC CHEMISTRY
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D.
Alkyl Halides
1.
There are some organic compounds where the hydrogens are
substituted by a halogen (–F, –Cl, —Br or —I). These compounds
are called ALKYL HALIDES.
NAMING ALKYL HALIDES:
i)
Attached F, Cl, Br and I atoms are called “fluoro”, “chloro”,
“bromo” and “iodo” groups. Use numbers to indicate the
position of attachment on the hydrocarbon chain.
ii)
If more than one of the same kind of halogen is present, use
the prefixes di, tri, tetra, etc.
iii)
If a compound contains both alkyl and halo groups, list the
attached groups in alphabetical order. Start numbering from
the end that gives the lowest set of numbers.
EXAMPLE X.4 NAMING ALKYL HALIDES
Problem: Name the following alkyl halides.
Solution:
CH3—CH—CH2—CH3
|
F
2–fluoro butane
CH3—CH—CH2—CH—CH3
|
|
Cl
Cl
2,4–dichloro pentane
CH2—CH3
|
CH3—CH—C—CH2—CH3
|
|
Br F
2–bromo–3–ethyl–3–fluoro pentane
UNIT X — ORGANIC CHEMISTRY
2.
PROPERTIES OF ALKYL HALIDES
 Alkyl halides tend to be insoluble in water.
 Compounds with many fluorine atoms tend to be unreactive.
 Chloro and bromo compounds are susceptible to chemical
attack, but require relatively drastic conditions. Iodo
compounds are more reactive.
Assign 17-20ace
10
UNIT X — ORGANIC CHEMISTRY
11
E.
Multiple Bonds
1.
Carbon atoms can form up to four bonds but it can form multiple
bonds with other carbon atoms. When a carbon shares 4 electrons
with a neighbouring carbon a DOUBLE BOND is formed and
when is shares 6 electrons with a neighbouring carbon a TRIPLE
BOND is formed.
An ALKENE is an organic compound containing a carbon–
carbon double bond.
An ALKYNE is an organic compound containing a carbon–
carbon triple bond.
NAMING ALKENES AND ALKYNES:
i)
If a double bond is present, change the “ANE” ending of the
parent hydrocarbon to “ENE”.
If a triple bond is present change the “ANE” ending of the
parent hydrocarbon to “YNE”.
ii)
Use a number to indicate the lower numbered carbon atom
involved in the bond. The number goes immediately in
front of the name of the parent hydrocarbon, separated by a
hyphen.
iii)
Number the parent hydrocarbon to give the double/triple
bond the lowest possible number. If the number is the same
starting from either end, start the numbering from the end
closest to the 1st branch point (where a group is attached).
UNIT X — ORGANIC CHEMISTRY
12
EXAMPLE X.5 NAMING ALKENES AND ALKYNES
Problem: Name the following alkenes and alkynes.
Solution:
H
CH2—CH3
\
/
C=C
/
\
CH  C—CH3
H
H
1–butene
propyne
CH2 = CH—CH—CH3
|
CH3
3– methyl–1–butene
2.
REMEMBER:
single bonds
double bonds
triple bonds
ANE
ENE
YNE
Assign 21-25ace
Alkenes and alkynes are called UNSATURATED hydrocarbons
because they have less hydrogen atoms than equivalent alkanes.
Alkanes are said to be saturated hydrocarbons because they contain
the maximum number of hydrogens possible.
3.
Whereas alkanes have flexible structures, alkenes have very rigid
structures. The double bonds “lock” the structure to prevent the
attached atoms from “twisting” around the double bond. The triple
bond in alkynes is also very rigid.
For an alkane, these two molecules are identical because the single
bond is free to rotate.
H3C CH3
|
|
CH3—CH—CH—CH2—CH3
2,3–dimethyl pentane
H3 C
|
CH3—CH—CH—CH2—CH3
|
CH3
2,3–dimethyl pentane
UNIT X — ORGANIC CHEMISTRY
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Because the double bond in an alkene cannot rotate or twist, these
two molecules are chemically different.
H3 C
|
CH3—C = C—CH2—CH3
|
CH3
H3C CH3
|
|
CH3—C = C—CH2—CH3
2,3–dimethyl–cis–2–pentene
2,3–dimethyl–trans–2–pentene
Notice that in the alkane both molecules have the same name
because they are the same molecule but in the alkene one is named
“CIS” and the other “TRANS”.
4.
CIS–TRANS isomerism is possible whenever a molecule has:
i)
a double bond present, AND
ii)
groups (other than a hydrogen atom) attached to each of the
carbons involved in the double bond.
In a “CIS” isomer, the two groups are on the SAME SIDE
of the double bond.
H3C
\
CH3
/
C=C
/
\
H
H
both CH3’s are on the
same side
In a “TRANS” isomer, the two groups are
“TRANSVERSE” to each other (that is, on opposite sides of
the double bond).
the CH3’s are on opposite
sides
H3C
\
H
/
C=C
/
\
H
CH3
Assign 26-28ace
UNIT X — ORGANIC CHEMISTRY
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F.
Aromatic Compounds
1.
Benzene, C6H6, is an important molecule having the following
structure.
The ring–like structure of benzene can be written in either of two
RESONANCE STRUCTURES, differing only in the placement
of the double bonds. Each resonance structure consists of
alternating single and double bonds. Benzene is frequently
represented as follows.
Benzene
2.
The benzene ring, also known as an “AROMATIC RING”, is
present in a large number of molecules and many molecules
contain two or more aromatic rings joined together.
An AROMATIC MOLECULE is a molecule containing one or
more benzene rings.
NAMING AROMATIC MOLECULES:
i)
The naming of simple aromatic compounds formed by
adding groups to a benzene ring is almost identical to the
naming procedure used for cyclic hydrocarbons.
ii)
When the benzene ring is attached to another hydrocarbon as
a substituent or group it is called a “PHENYL” group.
UNIT X — ORGANIC CHEMISTRY
15
EXAMPLE X.6 NAMING AROMATIC MOLECULES
Problem: Name the following aromatic molecules
Solution:
CH2—CH3
|
CH2—CH3
|
|
H3C
ethyl benzene
\
CH3
4-ethyl-1,2-dimethylbenzene
CH3—CH—CH2—CH3
|
2–phenyl butane
Assign 29-31ace
UNIT X — ORGANIC CHEMISTRY
16
G.
Functional Groups
1.
On some organic molecules, one or more of the hydrogens may be
substituted by an atom or a group of atoms. These substitutions
are called FUNCTIONAL GROUPS.
A FUNCTIONAL GROUP is a specific group of atoms which
exists in a molecule and gives a molecule an ability to react
in a specific manner or gives it special properties.
Hydrocarbons have a limited range of properties and uses.
Functional groups allow the addition of specific properties to a
molecule. For example, by carefully choosing the functional group
present in a molecule, a chemist can:
i)
make a molecule act as a base, an acid, or both;
ii)
give the molecule a particular solubility;
iii)
give a molecule a pleasant or unpleasant smell;
iv)
make a molecule react with specific chemicals;
v)
make a molecule explosive.
UNIT X — ORGANIC CHEMISTRY
2.
17
Different FUNCTIONAL GROUPS
a)
ALCOHOL
An ALCOHOL is an organic compound containing an –OH
group.
NAMING AN ALCOHOL:
i)
Number the hydrocarbon chain to give the LOWEST
possible number to the –OH group.
ii) Place the number immediately before the name of the
parent hydrocarbon separated by a dash.
iii) Indicate the presence of an –OH group by changing the
“e” ending of the hydrocarbon chain to “ol”.
CH3—OH
methanol
CH3—CH—CH2—CH3
|
OH
2–butanol
CH3—CH2—OH
ethanol
CH3—CH—CH2—CH2—CH—CH2—CH3
|
|
CH3
OH
6–methyl–3–heptanol
Assign 32-33ace
b) ALDEHYDES
An ALDEHYDE is an organic compound containing a
C=O group at the end of hydrocarbon chain.
The aldehyde group actually looks like
—CHO.
O
||
—C—H
or simply
UNIT X — ORGANIC CHEMISTRY
18
NAMING ALDEHYDES:
i)
Change the “e” ending of the parent hydrocarbon to
“al”.
ii)
If there are substituents attached, they are numbered
starting from the —CHO group.
O
||
H—C—H
methanal
(formaldehyde)
CH3—CHO
ethanal
CH3—CH2—CH2—CH—CHO
|
CH3
2–methyl pentanal
CHO
|
benzenal
c)
KETONES
A KETONE is an organic compound containing a C=O
group at a position OTHER THAN AT THE END of a
hydrocarbon chain.
The ketone group is represented by —CO—.
NAMING KETONES:
i)
Number the hydrocarbon chain to give the LOWEST
possible number to the —CO— group.
ii)
Place the number immediately before the name of the
parent hydrocarbon separated by a dash.
UNIT X — ORGANIC CHEMISTRY
iii)
19
Change the “e” ending of the parent hydrocarbon to
“one”.
O
||
CH3—C—CH3
or CH3COCH3
propanone
(acetone)
CH3CH2COCH2CH2CH3
O
||
3–hexanone
cyclohexanone
d)
ETHERS
An ETHER is an organic compound in which an oxygen
joins two hydrocarbon groups. The ether group is
represented by —O—.
NAMING ETHERS:
i)
Name the shorter hydrocarbon chain. Replace the
“ane” with “oxy”.
ii)
Number the parent hydrocarbon so that the ether group
has the LOWEST possible number.
iii)
Use a number separated by a dash to indicate the
location of the ether group.
CH3CH2—O—CH2CH3
ethoxy ethane
CH3—O—CH2CH2CH3
1–methoxy propane
CH3
|
CH3—C—CH2—CH2—O—CH3
|
CH3
1–methoxy –3,3–dimethylbutane
UNIT X — ORGANIC CHEMISTRY
e)
20
AMINES
An AMINE is an organic compound containing an —NH2
group.
NAMING AMINES:
i)
Number the parent hydrocarbon so that the amine has
the LOWEST possible number.
ii)
Name the —NH2 group “amino” and indicate the
location of the amine group by a number followed by a
dash.
CH3—CH2—NH2
amino ethane
f)
CH3—CH—CH2—CH3
|
NH2
2–amino butane
AMIDES
An AMIDE is an organic compound containing a —CONH2
group.
O
||
—C—NH2
UNIT X — ORGANIC CHEMISTRY
21
NAMING AMIDES:
i)
Number the parent hydrocarbon from the —CONH2
group.
ii)
Remove the "e” ending and add “amide” to the end of
the name.
CH3—CONH2
CH3—CH2—CH2—CH2—CH2—CONH2
ethanamide
hexanamide
CH3
|
CH3—C—CH2—CONH2
|
CH3
g)
3,3–dimethylbutanamide
CARBOXYLLIC ACIDS
A CARBOXYLLIC ACIDS is an organic compound
containing a —COOH group.
O
NAMING CARBOXYLLIC ACIDS:
||
—C—OH
i)
Number the parent hydrocarbon from the —COOH
group.
ii)
Remove the "e” ending and add “oic acid” to the end of
the name.
CH3COOH
HCOOH
ethanoic acid
(acetic acid)
methanoic acid
(formic acid)
CH3—CH2—CH2—COOH
butanoic acid
(butyric acid)
UNIT X — ORGANIC CHEMISTRY
h)
22
ESTERS
An ESTER is an organic compound containing a —COO—
group.
O
||
—C—O—
NAMING ESTERS:
i)
The hydrocarbon attached directly to the carbon side of
the —COO— group has its “e” changed to “oate”.
ii)
The hydrocarbon chain attached to the oxygen side of
the —COO— group is named as an alkyl group.
CH3—CH2—CH2—COO—CH3
methyl butanoate
HCOO—CH3—CH2—CH2—CH3
butyl methanoate
CH3—CH2—COO—CH2—CH3
ethyl propanoate
CH3—COO—CH2—CH2—CH3
propyl ethanoate
SUMMARY OF FUNCTIONAL GROUPS
NAME
FUNCTIONAL
GROUP
NAME
FUNCTIONAL
GROUP
alkene
C=C
ether
—O—
alkyne
CC
amine
—NH2
halide
–F, –Cl, –Br, –I
amide
—CONH2
alcohol
—OH
carboxyllic acid
—COOH
aldehyde
—CHO
ester
—COO—
ketone
—CO—
aromatic ring
Assign 37 odd That’s all folks!