Lecture No.11Principle of Organic

ChemistryDone by

Lecturer:Amal Abu- Mostafa

Refinery and tank storage facilities, like this one in Texas, are needed to change the hydrocarbons of crude oil to many different petroleum products. The classes and properties of hydrocarbons

form one topic of study in organic chemistry

Organic chemistry is the chemistry of compounds containing carbon.

The Bonding of Carbon: Carbon is in Group IVA (4A) of the

periodic table. It has four valence electrons. To fill its octet, it requires four

additional electrons, which can be obtained through the formation of four covalent bonds.

Organic chemistry:

Carbon forms single, double, and triple bonds to achieve a filled octet.

Therefore, the possible bonding combinations for carbon are as follows:

The Bonding of Carbon:

unique feature of carbon is its ability to form strong

covalent bonds to each other while at the same time

bonding strongly to atoms of other nonmetals, to

form chains and rings of various lengths.

Carbon is the only element capable of forming stable

extend chains, for example: CH3- (CH2)n- CH3

The simplest organic compounds are: hydrocarbons, compounds containing only carbon and hydrogen.

All other organic compounds—for example, those containing O, N, and the halogen atoms—are classified as being derived from hydrocarbons.

HYDROCARBON

1. Saturated hydrocarbons are hydrocarbons that contain only single bonds between the carbon atoms. Saturated hydrocarbon molecules can be cyclic or acyclic.

2. Unsaturated hydrocarbons are hydrocarbons that contain double or triple bonds between carbon atoms.

3. Aromatic hydrocarbons are hydrocarbons that contain benzene rings or similar features.

Hydrocarbons can be separated into three main groups:

The alkanes are saturated hydrocarbons. The cycloalkanes are cyclic saturated hydrocarbons.

The simplest hydrocarbon, an alkane called methane, consists of one carbon atom to which four hydrogen atoms are bonded in a tetrahedral arrangement.

Alkanes and Cycloalkanes:

The alkanes, also called paraffins, (have the general formula CnH2n+2. )

For n=1, methane, the formula is CH4; for n=2, C2H6;

for n=3, C3H8; and so on.

The Alkane Series:

Those are called straight-chain or normal alkanes. The structural formulas for the first four straight chain alkanes are shown.

The alkanes occur in what is called a homologous series, which is a series of compounds in which one compound differs from a preceding one by a fixed group of atoms CH2.

This table lists the melting points and boiling points of the first ten straightchain alkanes (n=1 to n=10).

In addition to the straight-chain alkanes, branched-chain alkanes are possible.

For example, isobutane (or 2-methylpropane) has the structure

Butane and isobutane are constitutional (or structural) isomers, compounds with the same molecular formula (C4H10) but different structural formulas.

Constitutional Isomerism and Branched-Chain Alkanes:

Isomers of pentane Note that each isomer is

a different compound with a different boiling point.

Another Example:

The general formula for cycloalkanes is CnH2n

This Figure gives the names and structural formulas

for the first four members of the cycloalkane

series.

In the condensed structural formulas, a carbon atom

and its attached hydrogen atoms are assumed to be at

each corner.

Cycloalkanes:

Cycloalkanes:

The IUPAC rules for naming organic compounds follow a regular

pattern.

The names of all saturated hydrocarbons, for example, end in –

ane.

For each family there is a rule for picking out and naming the

parent chain or parent ring within a specific molecule.

[The International Union of Pure and Applied Chemistry (IUPAC)]

IUPAC Nomenclature of Alkanes:

1- Find the longest continuous chain of carbon atoms and use the name of this chain as the base name for compound.

2- Number the carbon atom in the longest chain beginning with end of the chain that is nearest to the substituent.

Any branch that consists only of C and H and has only single bonds is called an alkyl group and the name of all alkyl groups end in - yl

3- Name and give location of each substituent group

4- when 2 or more substituent are present, list them in alphabetical order

IUPAC Rules for naming the alkanes:

3- Chloro- 4- methyl hexane

2,3-dimethyl butane

3- ethyl- 2- methyl pentane

Examples:

2,2-dimethyl butane 2-methyl pentane

3-methyl hexane

Examples:

Alkanes are relatively unreactive at room temperature.

They don’t react at room temperature with acids or bases or

even oxidizing and reducing agents, because of the strength of

the bonds C-C and C-H.

Alkanes burn in air to give water and oxides of carbon (CO2

and CO), H2O

2C2H6 + 7O2 4 CO2 + 6H2O

Chemical properties of alkans:

Another type of alkane reaction is cracking When heated at high temperatures in the absence of air, alkanes

“ crack” , meaning that they break up into smaller molecules. For example: ethane is cracked to give ethene in the presence

of a catalyst C2H6 high temp. C2H4 + H2

Also, Alkane undergo substitution reaction C2H6 + Cl2 CH3CH2Cl + HCl But, this type of reaction is difficult to control, and yield

different compounds such as C2H4Cl2, C2H3Cl3

Chemical properties of alkans:

Unsaturated hydrocarbons are hydrocarbons that consist one or more multiple bond (double or triple bond).

1)Alkenes: unsaturated hydrocarbons that contain double bond.

Open chain alkenes have the General Formula : CnH2n as: C3H6, C4H8, C6H12

The simplest alkenes is ethene or ethylene CH2=CH2

Next one is propene (propylene) CH3-CH=CH2

Example: CH3-CH2-CH=CH2 [1-butene] CH3-CH=CH-CH3 [2-butene].

Unsaturated Hydrocarbons:

Unsaturated hydrocarbon that contain triple bond

C C General formula for alkynes (when open chain): CnH2n-2

e.g. : C2H2, C3H4, C4H6

Simplest alkyne is ethyne or (acetylene) Examples:

1- propyne 1- butyne

2(Alkynes:

A double bond has more electron density than a single bond.

Both alkenes and alkynes undergo addition reactions. (e.g. addition of H2 to alkene yeild alkane) CH2=CH2 + H2 Pt or Ni CH3-CH3

Similar reaction occur with alkyne but the product is alkene then followed by alkane.

+ H2 Pt H2C=CH2 Pt CH3-CH3

ethyne ethene H2 ethane

Additional reaction of Alkenes and Alkynes:

1- addition of HBr H2C=CH2 + HBr CH3-CH2Br

2- Addition of H2O

H2C=CH2 + H2O acid catalyst CH3-CH2OH

3- Addition of Cl2:

+ Cl2 Cl2

Other addition reaction:

Aromatic hydrocarbons usually contain benzene rings: six-membered rings of carbon atoms with alternating carbon–carbon single and carbon–carbon double bonds.

The electronic structure of benzene can be represented by resonance formulas.

Benzene:

Aromatic Hydrocarbons:

Simple benzene-containing hydrocarbons that have one group substituted on a benzene ring, for example:

When two groups are on the benzene ring, three isomers are possible. The isomers may be distinguished by using the prefixes ortho- (o-), meta- (m-), and para- (p-).

For example:

Examples of Aromatic Hydrocarbons :

It is sometimes preferable to name a compound containing a benzene ring by regarding the ring as a group in the same manner as alkyl groups, (phenyl group, C6H5—)

For example :Diphenylmethane

Examples of Aromatic Hydrocarbons :

A functional group is a reactive portion (part) of a molecule that undergoes predictable reactions.

Organic compounds containing oxygen: Examples are alcohols, ethers, aldehydes, ketones,

carboxylic acids, and esters.

1) Alcohols: They are molecules that contain OH group attached to a

carbon atom which in turn attached to 3 other groups by single bonds.

Functional Groups:

Alcohols are named by IUPAC rules similar to those for the hydrocarbons, except that the stem name is determined from the longest chain containing the carbon atom to which the -OH group is attached.

Some examples of alcohols are:

H

1-Butanol 2- butanol 2- Methyl-2-Propanol (a primary alcohol) (a secondary alcohol) (a tertiary alcohol)

Alcohol with 2 OH groups are: called glycol.

Ethylene glycol (IUPAC name: 1,2-ethanediol)

Some examples of alcohols are:

Alcohol with 3 OH groups are: called glycerol

IUPAC name:(1,2,3-propanetriol)

Some examples of alcohols are:

An ether is a compound formally obtained by replacing both H atoms of H2O by the hydrocarbon groups R and R\.

R-O-R\. CH3-O-CH3 Dimethyl ether CH3-O-C2H5 Ethyl methyl ether (important for surgery

operations) C2H5-O-C2H5 Diethyl ether Is a volatile liquid used as a solvent and as an anesthetic.

2 (Ethers:

Aldehydes and ketones are compounds containing a carbonyl group.

A) An aldehyde is :a compound containing a carbonyl group with at least one H atom attached to it.

3 (Aldehydes and Ketones:

Propionaldehyde (propanal)

The aldehyde function is usually abbreviated - CHO,

And the structural formula of acetaldehyde is written CH3CHO.

A ketone is a compound containing a carbonyl group

with two hydrocarbon groups attached to it.

The ketone functional group is abbreviated – CO –, and the

structural formula of acetone is written CH3COCH3.

Examples:

B) Ketones:

You first locate the longest carbon chain containing the carbonyl group to get the stem hydrocarbon name.

Then you change the -e ending of the hydrocarbon to -al for aldehydes

And -one for ketones. In the case of aldehydes, the carbon atom of the -CHO

group is always the number-1 carbon. In ketones, however, the carbonyl group may occur in

various nonequivalent positions on the carbon chain, so, the position of the carbonyl group is indicated by a number before the stem name.

Aldehydes and ketones are named according to IUPAC rules similar to those for naming alcohols.

A) A carboxylic acid: is a compound containing the carboxyl group, -COOH.

These compounds are named by IUPAC rules like those for the aldehydes, except that the ending on the stem name is -oic, followed by the word acid.

The carboxylic acids are weak acids. Examples: Butyric acid (butanoic acid)

4 (Carboxylic Acids and Esters :

These red ants, like other ants, make the simplest of the organic acids, formic acid. The sting of bees, ants, and some plants contains formic acid, along with some other irritating materials. Formic acid is HCOOH.

The general structure is: Examples: 1) Ethyl acetate IUPAC(ethyl ethanoate)

2) Methyl acetate IUPAC (methyl ethanoate)

Esters are important in soap industry.

B) An ester is :a compound formed from a carboxylic acid, RCOOH, reacting with an alcohol, ROH .

Most organic bases are amines.

A) Amines: are compounds that are structurally derived by replacing one or more hydrogen atoms of ammonia with hydrocarbon groups.

Examples: Ethyl amine (a primary amine) Dimethyl amine (a secondary amine)

Trimethyl amine (a tertiary amine)

5 (Organic Compounds Containing Nitrogen:

Amides are: compounds derived from the reaction of ammonia, or of a primary or secondary amine, with a carboxylic acid.

For example:

B) Amides:

Summary of the Functional Groups: