January 13 1 Organic Chemistry
20.1 Organic Chemistry
An Introduction to nomenclatures, structures and reactions
Dr. Fred Omega Garces Chemistry 201 Miramar College
January 13 3 Organic Chemistry
Outline Organic Chem and the Carbon atom Atoms in Organic Compounds; Number of bonds
Representing Organic Compounds
Family Tree and Formula
Prefixes and suffixes
Degrees of Carbon Isomers
Alkyl Group
IUPAC nomenclature
Substituents
Alkenes and Alkynes ... geometric isomers
Aromatic compounds and nomenclature
Functional Group
January 13 4 Organic Chemistry
What is Organic Chemistry ?
Organic Chemistry:
Study of carbon containing compounds.
Everything else is considered inorganic. Over 30 million chemicals from 120 known elements.
800 thousands are inorganic the rest are organic chemicals.
Why are there so many organic compounds?
January 13 5 Organic Chemistry
The magic Carbon atom
Difference between organic and inorganic is C-atom ability to form very long chain
Inorganic compound will become unstable after with 12 or more atoms.
C-atoms ability to form very strong covalent bond means molecules can possess 100 or more atoms
January 13 6 Organic Chemistry
Evolution of Organic Chemistry “Can man artificially create a living animal from chemicals ?”
- magnitude of question concerning organic compound
Prior to 1828, organic compounds can only be obtained from living organism
Fredrick Wohler prepared urea, a chemical in urine (an organic compound)
NH4Cl + AgNCO g NH2-CO-NH2 + AgCl
Now a days the bulk of organic compounds
is manufactured in the lab.
C
H2N NH2
O
January 13 7 Organic Chemistry
Source of Organic Compound Organic chemicals isolate from nature. Nature
has her huge laboratory and is constantly synthesizing chemicals through biosynthesis.
Today we can manufacture these same chemicals in the lab
Mescaline
Caffeine Tetrahydrocannabinol THC
HO
H
H
HH
H
Ethanol
January 13 8 Organic Chemistry
Lewis Dot Structure: Number of bonds for nonmetal atom
Lewis Dot Structure and VSEPR: revisited
H C N O X Val. e- 1 4 5 6 7
# Bonds 1 4 3 2 1 H-H CH4 NH3 H2O H-Cl
January 13 9 Organic Chemistry
Forms of Carbons Carbons with single bond :
Methane, CH4 Tetrahedral 109.5° sp3
Carbons with double bonds ethene, C2H6 Trig. planar 120° sp2
Carbons with triple bonds
Ethyne C2H2 Linear 180° sp
HC CH
January 13 10 Organic Chemistry
Structure - Ways of presenting organic Compounds
Consider: Ethanol and dimethylether C2H6O Molecular formula - indicate type and number of atoms
C2H6O C2H6O Structure formula - shows connectivity of atoms in a compound
Ethanol Dimethylether
Condense formula - shows connecting group of atoms in a compound Ethanol, CH3CH2OH Dimethylether, CH3OCH3
Shorthand notation - shows hydrocarbon as "R" and functional group as is. Ethanol R-OH Dimethylether R-O-R’
Stick (Skeleton) form - shows hydrocarbons as lines with functional group Ethanol Dimethylether
Isomers - Compounds that have the same formula but different structures Ethanol and dimethylether have the same formula but are different compounds
and therefore possesses different properties Ethanol is the drinkable alcohol, while dimethyl ether was used as an anesthetic.
OH O
January 13 11 Organic Chemistry
Functional Group Name -Suffix group Example
1 Aliphatics -ane, -ene,-yen
, , , , propane, propene, proyne
2 Alcohol -ol =
propanol3 Ether - ether ,
ethylpropylether4 Aldehydes -al
, propanal
5 Ketones -one
, propanone
6 Carboxylicacid
-oic acid
, propanoic acid
7 Ester -ate,
methyl propanoate8 amine -amine
, triethyl amine
9 amide -amide
, N-methylpropamide
C C C C C C
OHOH
R O R ' O
R C OH C O
H
R CO
R 'CO
R CO
OH CO
OH
R CO
O R 'CO
O
R NR '
R ' N
NR '
R 'RC
ONHC
O
January 13 12 Organic Chemistry
Organic Compounds; the Family Tree.
Organic Compounds
cyclo Aliphatics
Hydrocarbons Heteroatoms
Aromatic Aliphatics
Alkane
Alkene
Alkyne
O
CH 3 CH 3
C NH
O
January 13 13 Organic Chemistry
Alkanes CnH2n+2
Hydrocarbons with only single bonds
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
Pentane C5H12
The Alkanes
January 13 15 Organic Chemistry
Degree of Carbon
a) primary carbons, 1° -
carbons bonded to only one other carbon
b) secondary carbons, 2° -
carbons bonded to two other carbons
c) tertiary carbons, 3° -
carbons bonded to three other carbons
d) quaternary carbons, 4° -
carbons bonded to four other carbons
C
CH2
CH3
CH
CH3
CH3
CH3CH3
January 13 16 Organic Chemistry
Prefix and the Number of Carbons # of
CMolecularFormula
Prefix Alkanename
Structure and isomers
groupname
1 CH4 meth- methane CH4 methyl2 C2H6 eth- ethane ethyl3 C3H8 prop- propane propyl, i-propyl4 C4H10 but- butane
, butyl, iso-butyl
sec-butyl, tert-butyl5 C5H12 pent- pentane
, ,
pentyl
6 C6H14 hex- hexane etc... -
7 C7H16 hept- heptane -8 C8H18 oct- octane -9 C9H20 non- nonane -
10 C10H22 dec- decane -
January 13 17 Organic Chemistry
Isomers are molecules with the same chemical formula but different structural formula.
Pentane (C5H12) n-pentane, iso-pentane, neo-pentane
Hexane (C6H14) n-hexane 2-methylpentane 3-methylpentane
2,3-dimethylbutane 2,2-dimethylbutane
Isomers
January 13 18 Organic Chemistry
Alkyl group (in naming scheme) Alkyl group - An important idea in the naming scheme is the group of atoms
attached to a carbon chain. These have yl - suffix.
First 5 alkyl groups and their isomers:
1. Methyl 2. Ethyl 3. Propyl: n-propyl, isopropyl
4 .Butyl: n-butyl, sec-butyl, iso-butyl, tert-butyl
5. Pentyl: n-pentyl, sec-pentyl, iso-pentyl, neo-butyl
(Assignment, write the stick figures of these alkyl groups
H
HCH
H
H
HH
C
H
HC C
H
H H
HH
HC C
H
H
H H
H
methane g methyl ethane g ethyl
. .
H3C
C
CH3
CH H
H CH3
H2CCH2
H2C CH3
CH2
H2CH2C
CH3 CH2
H3C CHCH3
H3C
CH
CH3
CH2C
H3C CH3H3C
January 13 19 Organic Chemistry
IUPAC Nomenclature Rules of the game: Alkane (CnH2n+2)
1. Find the longest continuous chain of carbon atoms. Assign this chain as the parent name . 2. Determine the substituents (groups) attached to the parent chain 3. Assign attachment position of group to main chain by starting at end closest to substituent group (or lowest number position).* 4. Identical groups attached to the main chain are designated with prefixes. 2-di, 3-tri, 4-tetra, 5-penta
5. Different groups attached to main chain are written in alphabetical order. 6. Alkyl halides: Halogen atoms (group) are designated as halogen prefix. F - Fluoro, Cl-Chloro, Br- Bromo, I- Iodo 7. Alkyl groups (see previous page)
• The numbering scheme should be chosen such that the sum of the position in which group are attached add up to the lowest sum.
http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/nomen1.htm
January 13 20 Organic Chemistry
• Consider the following hexane compound: Heptane (C7H16)
1. Pentane
2. Methyl
3. Carbon # 2 & # 3
4. 2,3 = position methyl = group pentane = parent name
5. Two methyl, g dimethyl
6. Name: 2,3-dimethylpentane
IUPAC nomenclature, an example
2 3
January 13 21 Organic Chemistry
• Alkyl • Methyl • Ethyl • Propyl: normal(n)-propyl, iso(i)-propyl • Butyl: normal(n)-butyl, iso(i)-butyl, sec(s)-butyl, tert(t)-butyl
• Halogens • Fluoro (F), Chloro (Cl), Bromo (Br), Iodo(I)
• Others • Nitro (NO2), Hydroxyl (OH), cyano (CN),
Common substituents
January 13 22 Organic Chemistry
Alkenes CnH2n • Alkynes CnH2n-2 Hydrocarbons with multiple bonds
- Ethene, C2H4 - Ethyne,C2H2
- Propene, C3H6 - Propyne, C3H4
Note:
If there is more than one multiple bond g poly unsaturated i.e.,
Alkenes and Alkynes
January 13 23 Organic Chemistry
More on Alkenes Geometric Isomers
Cis 2-butene Trans 2-butene Can’t rotate the double bond which makes these molecules unique compounds or specifically, Geometric isomers. Life example: 11-cis-retinal g all trans retinal
R
C
O
H
RH
Ohν
dark with enzyme Signals optic
nerve cell Visual pigment
(rhodopsin)
January 13 24 Organic Chemistry
more rules of the game: Alkene (CnH2n) -ene (suffix)
1. - ene suffix for alkenes 2. Main chain must include the double bond, the number one carbon is the carbon closest to the double bond.
3. position of double bond indicated by prefix numbering location. 4. For multiple double bonds : di = 2 double bonds tri = 3 double bonds
Alkyne (CnH2n-2) -yne (suffix) 1. - yne suffix for alkynes 2. Nomenclature rules are similar to that of alkenes
Nomenclature: Alkenes and Alkyne
2-propyl-1-pentene
2-methyl-hepta -1,3,5-triene
3-ethyl-4-methyl-1-hexyne
January 13 25 Organic Chemistry
1. Monosubstituted a. group benzene
nitrobenzene chlorobenzene bromobenzene ethylbenzene b. special names:
phenol toluene aniline benzaldehyde
2. Two substituted groups - use prefix for position
3. Three substituted groups - requires # scheme (lowest position scheme)
4. Benzene as a group - phenyl
Aromatics: nomenclature
NO2 Cl Br CH2CH3
OH CH3 NH2 CO
OH
Xo (ortho)
m(meta)p(para)
X1
2
34
5
X1
2
34
5
January 13 26 Organic Chemistry
Functional Group Name -Suffix group Example
1 Aliphatics -ane, -ene,-yen
, , , , propane, propene, proyne
2 Alcohol -ol =
propanol3 Ether - ether ,
ethylpropylether4 Aldehydes -al
, propanal
5 Ketones -one
, propanone
6 Carboxylicacid
-oic acid
, propanoic acid
7 Ester -ate,
methyl propanoate8 amine -amine
, triethyl amine
9 amide -amide
, N-methylpropamide
C C C C C C
OHOH
R O R ' O
R C OH C O
H
R CO
R 'CO
R CO
OH CO
OH
R CO
O R 'CO
O
R NR '
R ' N
NR '
R 'RC
ONHC
O
January 13 27 Organic Chemistry
What is the IUPAC names of the following alkanes: Draw the condensed structural formulas and the stick form for the following
i) 2,4-dimethyl-nonane ii) 3-methyl-4,4-diethyl-trans-2-heptene
iii) 1-ethyl-4-methyl-cyclohexane: Identify the functional group for each compound:
Organic: Examples
CO
CC
H3C
C
NH2
HO
HH
O
O
HO
C
ONH
H
CH3CO C CH3C
C
NH2HO
HH O
O
H O
CO
N HH
CH3