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