Organic Chemistry (1) Dr. Shatha Al-Aqeel
Organic Chemistry (1)
Dr. Shatha Al-Aqeel
• Course Number and Symbol: Chem. 240
• Credit hours: (2)
What is organic chemistry?
العضوية؟ • الكيمياء هي مادراسة • بأنها العضوية الكيمياء تعرف
الهيدروجينية الكربون مركباتHydrocarbons. ومشتقاتها
للكيمياء • القديم التعريف كان وقدالمركبات دراسة أنها العضويةالحية الكائنات في .Organicالموجودة
Hydrocarbons
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
sp3 hybridization in Methane
Bond lengths of Ethyne, Ethene, and Ethane
Isomers - compounds with the same molecular formula but different structures
Example: Butane and Isobutane
Structural Isomersالتركيبي التشابه
Butane IsobutaneBoiling point 0 -12Melting point -138 -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
Butane
CH3-CH2-CH2-CH2- CH3-CHH2C
CH3
H3C C
CH3
CH3
n-Butyl Isobutyl tert.Butyl
Propane
CH3-CH2-CH2- CH3-CH
CH3
n-Propyl Isopropyl
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.
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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
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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”, ….
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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.
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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.
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• 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.
• The common names isopropyl, isobutyl, sec-butyl, 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”.
Important note
• 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.
PHYSICAL PROPERTIES OF ALKANES
• 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.
BOILING POINTS
Preparation of alkanes
1- Hydrogenation of unsaturated hydrocarbon:
2- Reduction of alkyl halides
a- Hydrolysis of Grignard reagent
CH2 CH2
Ni or Pd or Pt / H2
200, 300CH3 CH3
CH3CH2Br + Mg2+ Dry ether CH3CH2MgBr
Grignard reagent
CH3CH2MgBrH3O
+
CH3CH3 + Mg(OH)Br
b- Reduction by metal and acid
c- From coupling with metal
d- Using cuprate method ( Gilman reagent )
CH3CH2CH2Br + Zn2+ H
+
CH3CH2CH3
CH3CH2CH2CH2Br1)LiAlH4 / Ether
CH3CH2CH2CH3
+ ZnBr
2) H3O+
CH3 Br2 + 2 Na CH3 CH3 + 2 NaBr
(CH3CH2)2CuLi + CH3Br CH3CH2CH3
Reaction of alkanes1- Halogenation
Free radical mechanism
RH + X2
Heat
or UV lightRX + HX
Alkyl HalideX2=Cl2 or Br2
Cl2 or Br2h
2 Cl
Cl + CH4 HCl + CH3
CH3 + Cl CH3Cl
CH4 + Cl2 + energy —> CH3Cl + HCl
if we have one type of carbon
CH4 + Cl2 + energy ——> CH3Cl + CH2Cl2 + CHCl3 + CCl4 + HCl
الهيدروكربون في االستبداالت زادت كلما التفاعل في الهالوجين نسبة زادت كلما
If we have different type of carbon
H H
H
H
+ Cl Cl
Cl
Cl
Cl Cl + ClHHeat or UV light
excess
+ Cl Cl +Heat or UV light
CH3 CH3
Br
CH3
BrCH3 CH3
major
Selectivity in halogenation reactions الهلجنة تفاعالت في االختيار
2- combustion of alkanes
160 kcal\mol for each methylene group
CH4 + 2 O2 CO2 + 2 H2O + 213 Kcal\mol
C2H6 + 7/2 O2 2 CO2 + 3 H2O + 373 Kcal\mol