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

Aliphatic Straight chainSaturatedAlkanesUnsaturatedAlkenesAlkynesCyclic Aromatic Cyclic

General Molecular Formula of Hydrocarbons

Classes of carbon and Hydrogen Primary carbon : CH 3 -CH 2 -CH 3 Secondary carbon : CH 3 -CH 2 -CH 3 Tertiary carbon : (CH 3 ) 2 -CH-CH 3 Hydrogens are also referred to as 1º, 2º or 3º according to the type of carbon they are bonded to.

Hybridization sp 3 Tetrahedral sp2 Trigonal Planar sp Linear

sp 3 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 Isomers التشابه التركيبي Butane Isobutane Boiling point Melting point

Pentane, C 5 H 12 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 Propane

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, NO 2 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. -NO 2 nitro - NH 2 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

b- Reduction by metal and acid c- From coupling with metal d- Using cuprate method ( Gilman reagent )

Reaction of alkanes 1- Halogenation Free radical mechanism CH 4 + Cl 2 + energy —> CH 3 Cl + HCl

if we have one type of carbon CH 4 + Cl 2 + energy ——> CH 3 Cl + CH 2 Cl 2 + CHCl 3 + CCl 4 + HCl كلما زادت نسبة الهالوجين في التفاعل كلما زادت الاستبدالات في الهيدروكربون If we have different type of carbon Selectivity in halogenation reactions الاختيار في تفاعلات الهلجنة

2- combustion of alkanes 160 kcal\mol for each methylene group