THEME: Chemical bonds and mutual THEME: Chemical bonds and mutual influence of the atoms in theinfluence of the atoms in the organic organic

compounds’ molecules.compounds’ molecules. Acidic and basic properties of theAcidic and basic properties of the

organic compounds. Classification of organic compounds. Classification of the organic reactions and reagents.the organic reactions and reagents.

associate. prof. Ye. B. Dmukhalska, assistant. I.I. Medvid

LECTURE № 1

Concept of organic chemistry.

Butlerov theory of structure of organic compounds..

Classification of organic compounds..

Nomenclature of organic compounds..

Types of the chemical bonds and their description

Hybridization of the atom orbitals: sp-, sp2-, sp3-.

Conjugate systems.

Inductive effect. Mesomeric effect.

Methods of ascertainment of the structure of organic compounds.

Acidic and basic properties of the organic compounds.Acidic and basic properties of the organic compounds.

Classification of the organic reactions and reagents.Classification of the organic reactions and reagents.

ContentsContents

We can designate the formula of organic compound next ways:

structural formula (complete, shorten, simply).molecular formula.

Complete structural formula:

C C C

H

H

H

H

H

H

H

C

H

H

H

C

C

C

C

C

C

H

H

H H

H

H

H

H

HHH

H

hexane butane

Shorten structural formula:

CH3—CH2—CH2—CH3

H2C

H2C

H2C

CH2

CH2

CH2

butane

hexane

Simply structural formula:

butane

hexane

Molecular formulas:

2 types:

ethanol C2H5OHC2H6O

Models of the molecule of methane

3. Classification of organic compounds

Functional group classification Name of class of organic compounds

Functional group General formula of class of organic compounds

Halogen carbonhydrates —F, —Cl, —Br, ––I R—Hal

Alcohols, phenols —OH R—OH

Thioalcohols, thiophenols —SH R— SH

Simple ethers —OR R—O—R

Aldehydes

Ketones

Carbon acids

Sulfoacids —SO3—H R—SO3—H

Complex ethers

Amides

Nitryles —C N R—C N

Nitrocompounds —NO2 R—NO2

Amines —NH2 R—NH2

C

O

H

R C

O

H

C

O

C

O

R R

C

O

OH

R C

O

OH

C O

O

C O

O

R R

C NH2

O

R C NH2

O

There are mono-, poly- and heterofunctional group in the structure of organic compounds:

Monofunctional group – contains only 1 functional group.

C2H5—OH

Polyfunctional group – contains several similar functional group.H2C

CH

H2C

OH

OH

OH

Heterofunctional group – contains several different functional group.

OH

C

O

H

All organic compounds concerning to the same class form the homological row – it is the row of organic compounds in which each next matter

differ —CH2— group from previous one. i.e. Alkanes

Methane CH4

Ethane C2H6

Propane C3H8

Butane C4H10

Pentane C5H12

Hexane C6H14

Heptane C7H16

Octane C8H18

Nonane C9H20

Decane C10H22

Undecane C11H24

Dodecane C12H26

Nomenclature of organic compounds

Trivial.Trivial.

Rational.Rational.

IUPAC (International Union of Pure and IUPAC (International Union of Pure and Applies Chemistry) nomenclature.Applies Chemistry) nomenclature.

Nomenclature of organic compounds had been formed during last centuries.There are:

Trivial nomenclature. At first organic compounds were named by chance, for example, because the natural sources of its receiving or their properties (citric acid, formic acid). Many trivial names of organic compounds are used nowadays.

Rational nomenclature. It was the first nomenclature in which the structure of molecule was considered.

CH4 CH3—CH3 CH3—CH2—CH3

methane methylmethane dimethylmethane

IUPAC nomenclature. The IUPAC system is the most rational and widely used system of nomenclature in organic chemistry. The most important feature of this system is that any molecular structure has only one name.

The IUPAC name of anyorganic compound consists of 3 parts: root.suffix (primary, secondary). prefix (primary, secondary).

1. Word root. It is the basic unit of the name. It denotes the number of carbon atoms present in the principal chain (the longest possible continuous chain of carbon atoms including the functional group and the multiple bonds) of the organic molecule. For chains from one to four carbon atoms, special word roots (based upon the common names of alkanes) are used but for chains of five or more carbon atoms, Greek number roots are used as given below:

2. Suffix. There are two types of suffixes:a) Primary suffix. А primary suffix is always added to the word root to indicate whether the carbon chain is saturated оr unsaturated. Type of carbon chain Primary

suffix General name

Saturated ane Alkane

Unsaturated with one double bond ene Alkene

Unsaturated with one triple bond yne Alkyne

Unsaturated with two double bonds diene Alkadiene

Unsaturated with two triple bonds diyne Alkadiyne

The following examples illustrate the usage of word roots and primary suffixes in naming of organic compounds:

Organic compound Word root

Primary suffix

IUPAC name

CH3CH2CH2CH3 But ane Butane

CH2=CHCH3 Prop ene Propene

CHCH Eth yne Ethyne

CH2=CH–CH=CH2 Buta diene Butadiene

CHCH–CHCH Buta diyne Butadiyne

b) Secondary suffix. А secondary suffix is added to the primary suffix to indicate the nature of the functional groups are present in the organic compound. Secondary suffixes of some important functional groups are given below:

The following examples illustrate the usage of the word root, primary suffix and secondary suffix in naming of the organic compounds:

Organic compound Word root

Primary suffix

Secondary suffix

IUPAC name

СН3СН2ОН Eth ane ol Ethanol

СН3СН2СН2NH2 Prop ane amine Propanamine

СН3СН2СН2COOH But ane oic acid Butanoic acid

СН3СН2СN Prop ane nitrile Propanenitrile

СН2=СНСНO Prop ene al Propenol

СНСНСOOН Prop yne oic acid Propynoic acid

3. Prefix.3. Prefix. There are two types of prefixes: There are two types of prefixes:a) Primary prefix.a) Primary prefix. АА primary prefix is used simply to primary prefix is used simply to distinguish cyclic from acyclic compounds.distinguish cyclic from acyclic compounds.For exampleFor example

Cyclo pent ane CyclopentanePrimary prefix Word root Primary suffix IUPAC name

If the prefix cyclo- is not used, it simply indicates that the compound is acyclic or with open chain.

b) Secondary prefix. In IUPAC system the nomenclature of the certain groups is not considered as functional groups but instead are treated as substituents, these groups are called secondary prefixes and are added order to denote the side chains or substituent groups. The secondary prefixes for some groups which are always treated as substituent groups:

The following examples illustrate the usage of word The following examples illustrate the usage of word root, primary and secondary prefixes and suffixes in root, primary and secondary prefixes and suffixes in naming of organic compounds:naming of organic compounds:

Organiccompound

Secondarprefix

Wordroot

Primarsuffix

IUPAC name

СН3СН2–Br Bromo eth ane Bromoethane

СН3–NO2 Nitro meth аnе nitromethane

С2Н5–O–С2Н5 Ethoxy eth аnе Ethoxyethane

In the case of carbocyclic compounds primary prefixes are also used. For example,

4-Bromo cyclo hex an (е) 1-ol 4-Bromocyclohexan-1-ol Secondary Primary Word Primary Secondary prefix prefix root suffix suffix

correct wrong Sum of the locants = 3 + 4 = 7 Sum of the locants = 4 + 5 = 9 Set of locants = 3, 4 Set of locants = 4,5

correct wrongSum of the locants = 2+ 2+ 4 = 8 Sum of the locants = 2+ 4+ 4 =

10Set of locants = 2,2,4 Set of locants = 2,4,4

Types of the chemical bonds and their description

In the molecule all atoms have influence on each other. The result of this influence is called electronic bonds.

There are 4 types of chemical bonds:Covalent bond. This is the main type of bond in organic

chemistry. It formed is between atoms with similar electronegativity. In this case common electronic cloud is formed.

C 4H H C

H

H

H+

Polar bond. This is a covalent bond between 2 atoms with different electronegativity in which electron pair is not shared equally. But the difference of electronegativity is not big.

CH3 Cl CH3 Cl

Ion bond. This is a bond between 2 atoms with different electronegativity (difference of electronegativity is very big).

NaCl → Na+ + Cl–

Donor-acceptor bond. This is a type of covalent bond, but it has different origin. In covalent bond a pair of electrons consists of 2 electrons from 2 atoms. But in donor-acceptor bond only one atom gives 2 electrons, but another atom accepts one electron.

HH N

H

H

+ H+ H N

H

H

donor

acceptor

Semipolar bond. This is a type of donor-acceptor bond, then one atom has 2 free electrons, and another atom has 6 electrons.

H3C

H3C

H3C

N + O H3C

H3C

H3C

N O+ -

Hydrogen bond. This bond is formed between atom of H+ and negative atom. This bond is designated as 3 points (…).

HH H

H-O ... H-O ... H-O

0,099 nm

0,176 nm

COH

CO

HO

...

...H3C CH3

O

Hybridization of atom orbitals: sp-, sp2-, sp3-

Atom orbital is the space where the atom can be. There are s–, p– and d–atom orbitals.

s-orbital

p-orbital d-orbital

spsp33–hybridization of atom orbitals. This –hybridization of atom orbitals. This hybridization is formed when s–orbital joined hybridization is formed when s–orbital joined to 3 p–orbitals.to 3 p–orbitals.

+

s-orbital p-orbitals sp3-hybridorbitals

The Carbon atom forms covalent bonds in the molecule of The Carbon atom forms covalent bonds in the molecule of organic compounds. There are 2 types of covalent bonds: organic compounds. There are 2 types of covalent bonds: - and - and -bonds.-bonds.-bond is formed after joining of two different atomic -bond is formed after joining of two different atomic orbitals (s- and p-orbitals) or two hybrid orbitals (sporbitals (s- and p-orbitals) or two hybrid orbitals (sp33--hybrid orbitals):hybrid orbitals):

C C

H H

HH

H H

spsp22–hybridization of atom orbitals. This –hybridization of atom orbitals. This hybridization is formed when s–orbital joined to hybridization is formed when s–orbital joined to 2 p–orbitals.2 p–orbitals.

+

s-orbital p-orbitals sp2-hybridorbitals

-bond is formed after joining of two identical s- or p-orbitals.

C C

H H

HH

H H

In organic compounds the atom of Carbon has hybrid orbitals. There are 3 main types of them:

sp–hybridization of atom orbitals. This hybridization sp–hybridization of atom orbitals. This hybridization is formed when s–orbital joined to p–orbital.is formed when s–orbital joined to p–orbital.

+

s-orbital p-orbital sp-hybridorbitals

Electronic effects in organic compounds In organic compounds there are 2 types of electronic

movement of electronic density:-inductive effect.-mezomeric effect.Inductive effect is the movement of electronic density by

-bonds. i.e. ’’’+ ’’+ ’+ + -

CH3—CH2—CH2—CH2ClStructural effects such as this that are transmitted through bonds are called inductive effects. The atom of Chlorine has larger electronegativity than the atom of Carbon. That’s why the atom of Chlorine takes electronic density, and electronic density of the molecule moves to atom of Chlorine. So:

’’’+ <’’+ <’+<+

But inductive effects are only part of the story. When nitric acid transfers its proton to water, nitrate ion is produced.

The negative charge is shared equally by all three oxygens. Stabilization of nitrate ion by electron delocalization increases the equilibrium constant for its formation.

Nitrate ion is stabilized by electron delocalization, which we can represent in terms of resonance between three equivalent Lewis structures:

Mezomeric effectMezomeric effect is the movement of electronic density by -bonds or conjugate systems.

Positive mezomeric effect have substituents that give electrons in a conjugated system, negative – that attract electron density from conjugated system.

Acidity and basicity of organic compounds.

Classification of the organic Classification of the organic reactions and reagents.reactions and reagents.

1. Accession reactions Electrophilic accession(AE)Nucleophilic accession(AN)Free radical accession (AR)Molecular accession

2) Substitution reactionsElectrophilic substitution (SE)Nucleophilic substitution (SN)Free radical substitution (SR)

3) Elimination reactions

4) Regrouping reactions

5) Oxidation-reduction reactions

The end