TYPES OF CHEMICAL REACTIONS LECTURE CLASSIFICATION, STRUCTURE, NOMENCLATURE AND PROPERTIES OF ORGANIC COMPOUNDS. TYPES OF CHEMICAL REACTIONS Lecturer: Iryna R. Bekus

Organic Chemistry – the chemistry of the hydrocarbons and their derivatives; the chemistry of carbon compounds. Bioorganic Chemistry was study structure and properties of compounds, which are in human body. Such as: proteins, lipids, hormones, carbohydrates, vitamins, enzyme, fats, at el.

CLASSIFICATION By structure of carbon chain:

Acyclic — compounds, that don’t contain any cycle in their molecules Acyclic — compounds, that don’t contain any cycle in their molecules. Saturated — compounds that contain only -bonds and nо  - bonds (simple – C – C – bonds). Alkanes — saturated hydrocarbons that contain only – C – C – and – C – H –  bonds. Unsaturated — compounds that contain -bonds and  - bonds (double bonds (– C = C –) or triple (– C  C – ) bonds, and simple – C – C – bonds).

Alkenes — unsaturated hydrocarbons thаt contain only one – C – C – double bond (– C = C –). Diene — unsaturated compounds thаt contain two double – C – C – bonds. Alkynes — unsaturated hydrocarbons thаt contain – C – C – triple bond (– C  C – ). Cyclic — organic compounds thаt contain any cycle in its molecules.

Carbocyclic - hydrocarbons containing а cycle that consists of only Carbon atoms. Cycloalkanes — saturated hydrocarbons containing а Carbon cycle. Cycloalkenes — ansaturated hydrocarbons containing а Carbon cycle. Arenes — aromatic compounds thаt contain benzoic ring. Heterocyclic - organic compounds thаt contain cycle between atoms of Carbon and other elements (S, O, N).

Functional Group is any part of an organic compound, which is not а carbon-hydrogen or carbon-carbon single bon.

By functional groups:

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. Heterofunctional group – contains several different functional group.

NOMENCLATURE Common (trivial) International (IUPAC – International Union of Pure and Applied Chemistry) system of nomenclature was first introduced in 1947.

General rules for IUPAC nomenclature: The IUPAC name of any organic compound essentially consists of three parts: word root; suffix; prefix. Thus, а complete IUPAC name of an organic compound consists of the following parts: Secondary prefix + Primary prefix + Word root + Primary suffix + Secondary suffix

There are two types of suffixes: Primary suffix. А primary suffix is always added to the word root to indicate whether the carbon chain is saturated оr unsaturated. The three basic primary suffixes are given below:

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

PREFIX There are two types of prefixes: Primary prefix. А primary prefix is used simply to distinguish cyclic from acyclic compounds. For example, in case of carbocyclic compounds, а primary prefix, cyclo is used immediately before the word root. Thus: Cyclopentane

Secondary prefix. In IUPAC system of nomenclature, certain groups are not considered as functional groups but instead are treated as substituents. These are called secondary prefixes.

Complete structural formula: butane hexane

Shorten structural formula: CH3—CH2—CH2—CH3 butane hexane

Types of organic reactions. All the organic reactions can be broadly classified into the following four types: (a) substitution reactions, (b) addition reactions, (c) elimination reactions, (d) rearrangement reactions.

CH3OH + CH3COOH  CH3COOCH3 + H2O (I) Substitution reactions which are brought about by nucleophiles are called nucleophilic substitution reactions: CH3OH + CH3COOH  CH3COOCH3 + H2O (II) Substitution reactions which are brought about by electropholes are called electrophilic substitution reactions: (III) Substitution reactions brought about by free radicals are called free radical substitution reactions: CH4 +Cl2 → CH3Cl +HCl

Addition reactions Addition reactions are of the following three types: Addition reactions brought about by nucleophiles are called nucleophilic addition reactions: Addition reactions brought about by electrophiles are called electrophilic addition reactions. Addition reactions brought about by free radicals are called free radical addition reactions.

Elimination reactions Elimination reactions. An elimination reaction is one that involves the loss of two atoms orgroups of atoms form the same or adjacent atoms of a substance leading the formation of a multiple (double or triple) bond: These are of two types: -Elimination reactions. -Elimination reactions.

Reactions involving the migration of an atom or a group from one atom to another within the same molecule are called rearrangement reactions.

Oxidation — а net decrease in the number of  bonds to hydrogen or electropositive element, or а net increase in the number of bonds to electronegative elements. А net loss of electrons. Reduction — а net increase in the number of  bonds to hydrogen or electropositive element, or а net decrease in the number of bonds to electronegative elements. А net gains electrons.

ALCOHOL In chemistry, an alcohol is an organic compound in which the hydroxyl functional group (-OH) is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms.

Systematic names In the IUPAC system, the name of the alkane chain loses the terminal "e" and adds "ol", e.g., "methanol" and "ethanol“

Classification of alcohols Alcohols with one hydroxyl group - monohydric alcohol Alcohols with two hydroxyl groups - dihydric alcohol Alcohols with three hydroxyl groups - trihydric alcohols Alcohols with four or more hydroxyl groups - polyhydric alcohols

The saturated monohydric alcohols have the general formula CnH2n+1OH or ROH. Their functional group is -OH. They can be further classified into: 1) Primary Alcohol Here the carbon atom bearing the hydroxyl group is attached to just one other carbon atom. 2) Secondary Alcohol Here the carbon atom bearing the hydroxyl group is attached to two other carbon atoms.

3)Tertiary Alcohol Here the carbon atom bearing the hydroxyl group is attached to three other carbon atoms.

Carbon atom joined to oxygen by a double bond Carbonyl Group                                            Carbon atom joined to oxygen by a double bond Ketones Aldehydes             

Aldehydes Comes from alcohol dehydrogenation Obtained by removing of a hydrogen from an alcohol                                                       

Aldehydes Both common and IUPAC names frequently used Common names from acids from which aldehydes can be converted                                                            

Aldehydes IUPAC Longest chain with aldehyde Drop “e” and add “-al” Acetaldehyde Propionaldehyde Phenylethanal

Ketones Naming: Drop “e”, add “-one” Many common names                                                                        Naming: Drop “e”, add “-one” Many common names Simplest is 3 carbons C. name: acetone IUPAC: propanone

Physical Properties of Aldehydes and Ketones Carbon-oxygen double bond is very polar Affects boiling points More than ethers (C-O bonds) Less than alcohols (C-OH bonds) Odors Low aldehydes very pungent High aldehydes pleasant odors (perfumes) Solubility Similar to alcohols and ethers Soluble up to about 4 carbons Insoluble after that

Preparation of Aldehydes Oxidation                                                                                                                               

Hydration of alkynes (Kucherov reaction). Reaction occurs by way of an enol intermediate formed by Markovnikov addition of water to the triple bond.

Oxosynthesis. Interaction of alkenes with carbone (II) oxide, at the higher temperature, pressure and presence of catalyst.

Preparation of Ketones Oxidation                                                                

Chemical Properties of Aldehydes and Ketones Both undergo combustion reactions Oxidation Aldehydes can be oxidized, ketones can’t See Tollen’s reagent Benedict’s reagent Fehling’s reagent  

Reactions of aldehyde oxidation With Tollens’ reagent – “silver mirror” reaction. With Fehling reagent: after heating red precipitate of copper (I) oxide formed.

Chemical Properties of Aldehydes and Ketones                                              Chemical Properties of Aldehydes and Ketones Reduction Variety of agents can reduce aldehydes and ketones to alcohols                                                                                                       

Chemical Properties of Aldehydes and Ketones Hydration Formaldehyde dissolves readily in water Acetaldehyde somewhat also Form hydrates                                                                              

Chemical Properties of Aldehydes and Ketones                                                                                 Chemical Properties of Aldehydes and Ketones Addition of Alcohols to Carbonyl Groups Hemiacetal Aldehyde + alcohol Hemiketal Ketone + alcohol

Chemical Properties of Aldehydes and Ketones Hemiacetals + HCl = acetal Hemiketal + HCl = ketal                                                              

Thank you for attention