Transcript Introduction to Organic Chemistry

Organic Chemistry (1)
Dr. Shatha Al-Aqeel
• Course Number and Symbol:
Chem. 240
• Credit hours: (2)
‫?‪What is organic chemistry‬‬
‫• ما هي الكيمياء العضوية؟‬
‫• تعرف الكيمياء العضوية بأنها دراسة مركبات‬
‫الكربون الهيدروجينية ‪Hydrocarbons‬‬
‫ومشتقاتها‪.‬‬
‫• وقد كان التعريف القديم للكيمياء العضوية أنها‬
‫دراسة المركبات الموجودة في الكائنات الحية‬
‫‪.Organic‬‬
Hydrocarbons
Hydrocarbons
Aromatic
Aliphatic
Straight chain
Saturated
Alkanes
Cyclic
Unsaturated
Alkenes
Alkynes
Cyclic
General Molecular Formula of
Hydrocarbons
Classes of carbon and Hydrogen
•
•
•
•
Primary carbon : CH3-CH2-CH3
Secondary carbon : CH3-CH2-CH3
Tertiary carbon : (CH3)2-CH-CH3
Hydrogens are also referred to as 1º, 2º or 3º
according to the type of carbon they are
bonded to.
Hybridization
3
sp
sp2
sp
•Tetrahedral
•Trigonal Planar
•Linear
sp3 hybridization in Methane
Bond lengths of Ethyne, Ethene,
and Ethane
Structural Isomers
‫التشابه التركيبي‬
Isomers - compounds with the
same molecular formula but
different structures
Example: Butane and Isobutane
Butane
Boiling point
0
Melting point
-138
Isobutane
-12
-145
Pentane, C5H12 has three chain isomers.
IUPAC Nomenclature
• IUPAC (International Union of Pure and
Applied Chemistry) names:
• 1- The unbranched alkanes (homologous
series)
• 2- Branched alkanes
Unbranched alkyl groups
Propane
CH3
CH3-CH2-CH2-
CH3-CH
Isopropyl
n-Propyl
Butane
CH3
CH3
CH3-CH2-CH2-CH2-
CH3 -CH
H2
C
H3C
C
CH3
n-Butyl
Isobutyl
tert.Butyl
NOMENCLATURE OF BRANCHED-CHAIN
ALKANES
• 1- Locate the longest continuous chain
of carbon atoms; this chain determines
the parent name for the alkane.
• 2- Number the longest chain beginning with
the end of the chain nearer the substituent.
3- Use the numbers obtained by application
of rule 2 to designate the location of the
substituent group.
The parent name is placed last; the
substituent group, preceded by the
number indicating its location on the chain,
is placed first.
22
4. When two or more substituents are
present, give each substituent a number
corresponding to its location on the
longest chain.
The substituent groups are listed alphabetically
regardless of their order of occurrence in the molecule. Cl
is called chloro, Br called bromo, I called iodo, NO2
called nitro, CN called cyano
23
5) When two or more substituents are
identical, indicate this by the use of the
prefixes di-, tri-, tetra-, and so on.
In case of deciding alphabetical order of many
substituent disregard multiplying prefixes such as
“di”and “tri”, “tetra”, “penta”, ….
24
6)When two substituents are present on the
same carbon, use the number twice.
7. When two chains of equal length compete for
selection as the parent chain, choose the
chain with the greater number of
substituents.
26
8. When branching occurs at an equal
distance from both ends of the longest
chain, choose the name that gives the
lower number at the first point of
difference.
27
• If any other substituents are found on the
parent chain, all these substituents are
arranged alphabetically.
•
•
•
•
•
•
-NO2 nitro
- NH2 amino
-CN cyano
- Cl Chloro
-Br bromo
- I iodo
• When the parent chain has both a halo and an
alkyl substituent attached to it, number the
chain from the end nearer the first
substituent.
Important note
• The common names isopropyl, isobutyl, secbutyl, tert-butyl are approved by the IUPAC for
the unsubstituted groups.
• In deciding on alphabetically order disregard
structure-defining prefixes that are written in
italics and separated from the name by a
hyphen. Thus “tert-butyl” precedes “ethyl”, but
“ethyl” precedes “isobutyl”.
PHYSICAL PROPERTIES OF ALKANES
• 1) At room temperature (rt, 25 °C) and 1 atm
pressure, the C1-C4 unbranched alkanes are gases;
the C5-C17 unbranched alkanes are liquids; the
unbranched alkanes with 18 or more carbon atoms
are solids.
BOILING POINTS
• The boiling points of alkanes increase
with molecular weight.
• Branching reduces the boiling point,
the more branching the lower the
boiling point.
• Alkanes are almost completely
insoluble in water.
Preparation of alkanes
1- Hydrogenation of unsaturated hydrocarbon:
Ni or Pd or Pt / H2
H2C
CH2
H3C
CH3
200, 300
2- Reduction of alkyl halides
a- Hydrolysis of Grignard reagent
CH 3CH 2Br
+
2+
Mg
Dry ether
CH 3CH 2MgBr
Grignard reagent
CH 3CH 2MgBr
H3 O
+
CH 3CH 3
+
Mg(OH)Br
b- Reduction by metal and acid
+
CH 3CH 2CH 2Br
+
H
2+
Zn
CH 3CH 2CH 2CH 2Br
CH 3CH 2CH 3
1)LiAlH 4 / Ether
2) H 3O
+
+
ZnBr
CH 3CH 2CH 2CH 3
c- From coupling with metal
2 H3C
Br
+
2 Na
H3C
CH3
+
2 NaBr
d- Using cuprate method ( Gilman reagent )
(CH3CH2)2CuLi
+
CH3Br
CH3CH2CH3
Reaction of alkanes
1- Halogenation
RH
+
Heat
X2
or UV light
X2=Cl 2 or Br 2
+
RX
Alk yl Halide
HX
Free radical mechanism
CH4 + Cl2 + energy —> CH3Cl + HCl
Cl 2 or Br2
Cl
+ CH4
CH3 + Cl
h  
2 Cl
HCl
CH3Cl
+
CH3
if we have one type of carbon
H
H
Cl
Heat or UV light
H
+
Cl
Cl
Cl
excess
H
+
Cl
HCl
Cl
CH4 + Cl2 + energy ——> CH3Cl + CH2Cl2 +
CHCl3 + CCl4 + HCl
‫كلما زادت نسبة الهالوجين في التفاعل كلما زادت االستبداالت في الهيدروكربون‬
If we have different type of carbon
Selectivity in halogenation reactions ‫االختيار في تفاعالت الهلجنة‬
Heat or UV light
H3C
CH3
+
Cl
Cl
H3C
Br
major
CH3
+H3C
Br
2- combustion of alkanes
CH4
+
2 O2
CO 2
C2 H6
+
7/2 O 2
2 CO 2
+
+
2 H 2O
3 H 2O
+
213 Kcal\mol
+
373 Kcal\mol
160 kcal\mol for each methylene group