INTRODUCTION TO ORGANIC CHEMISTRY; SATURATED HYDROCARBONS.

INTRODUCTION TO ORGANIC CHEMISTRY; SATURATED HYDROCARBONS

Organic Chemistry – science that deal generally with compounds of carbon

–fats, proteins, carbohydrates–fabrics–wood and paper products–plastics–medicinals

Carbon atom is central to all organic compounds

What makes carbon special?

unique ability to bond to itself in long chains and rings;

ability to form strong covalent bonds with a variety of elements (H, O, N, S, P, halogens)

Carbon atom: C atomic number 6

electron structure 1s22s22p2

stable isotopes 12C and 13C

carbon has several radioactive isotope

Carbon has four valence electrons

1s2, 2s2, 2p2

C

C

Carbon forms four single covalent bonds by sharing electrons with other atoms.

H

HH H

CH

HH H

Carbon forms four single covalent bonds by sharing electrons with other atoms.

A pair of electrons can be shared between two carbon atoms.

One covalent bond can be formed between two carbon atoms.

single bond

C C

Single covalent bond can be formed between two carbon atoms C C

single bond

A dash represents a covalent bond.

Two covalent bonds can be formed between two carbon atoms.

double bond

C C

Two covalent bonds can be formed between two carbon atoms.

C Cdouble bond

Three covalent bonds can be formed between two carbon atoms.

triple bond

C C

Three covalent bonds can be formed between two carbon atoms.

C Ctriple bond

Organic compound

s

Saturated (only single bonds)

Unsaturated (double or triple bonds)

The types of molecular formulas and molecular models

H

H

H

H

C.... ....

C

H

HH

H

structural formula

C2H6

CH4

Lewis formul

a

molecular

formula

CH3CH3condensed structural formula

CLASSES OF ORGANIC COMPOUNDS

CLASSES OF ORGANIC COMPOUNDS (cont.)

HYDROCARBONS

compounds that are composed only of carbon and hydrogen atoms bonded to each other by covalent bonds

Sources: fossil fuels - natural gas, petroleum, coal

Hydrocarbons

Aromatic (contain the benzene

ring)

Aliphatic (open-chain and

cyclic)

Alkanes Alkenes Alkynes

Cycloalkanes Cycloalkenes UNSATURATED

SA

TU

RA

TED

ALKANES (paraffins, saturated hydrocarbons)straight or branched-chain hydrocarbons

with only single covalent bonds between the carbon atoms

Homologous series – each member of a series differs from the next member by a CH2 group.

General formula (for open chain alkanes): CnH2n+2; n – number of carbon atoms in the molecule

ISOMERISM

Isomerism – phenomenon of two or more compounds to have the same molecular formula but different structural arrangement

Isomers – compounds that have the same molecular formula but different structural formulas

C

H

HH

H

line structure form of

methane

CH4

space filling form of

methane

There is 1 possible structure for CH4.

19.419.4

CH3CH3

line structure form of ethane

C

H

CH

H

H

H

H

space filling form of ethane

There is 1 possible structure for C2H6.

19.4

line structure form of propane

C

H

CH

H

C

H

H

H

H

H

space filling form of propane

CH3CH2CH3

There is 1 possible structure for C3H8.

19.4

C C CC

H

H

H H

H

HH

H

H

H

line structure form of butane

CH3CH2CH2CH3 space filling form of butane

There are 2 possible structures for C4H10

unbranched chain19.4

C C C

C

H

H

H

H H

HH

H H

H

line structure form of 2-methyl

propane

CH2CHCH3

CH3

branched chain

space filling form of 2-methyl

propane

branched chain

There are 2 possible structures for C4H10.

19.4

normal butane (n-butane) C4H10

2 –methyl propane

C4H10

C C CC

H

H

H H

H

HH

H

H

H

C C C

C

H

H

H

H H

HH

H H

H

m.p. –138.3oC

b.p. 0.5oC

m.p. –159.5oC

b.p. – -11.7oC

Normal butane and 2-methyl propane are isomers.

Isomers are compounds with the same molecular formula but different structural formulas.

Pentane (C5H12) has 3 isomers.

This is the carbon skeleton with the longest continuous carbon chain. It is the first isomer of pentane.

C C C C C

n-pentane

C C C C C

H

H

H

H

H

H

HH

H

H

H

H

Hydrogen is added to each carbon to form four bonds.


2-methylpentane

To form the next isomer write a four carbon chain.

C C C CC C C C

C

Add the fifth carbon atom to either of the middle carbon atoms.

C C C C

C


C C C C H

CH

H

H

H

HHH

H

H

H

H


2,2-dimethylpropane

To form the third isomer write a 3 carbon chain.

C C C

Add the remaining two carbon atoms to the central carbon atom.

C C C

C

C


C C C

C

C

HHH

HHH

H

H

H

H

H

SATURATED HYDROCARBONS

NAMING ORGANIC COMPOUNDS

Used to: trivial names

Examples: wood alcohol – methanol; marsh gas – methane; alcohol or grain alcohol – ethanol; etc.

Now: internationally accepted and systematic method - IUPAC system (International Union of Pure and Applied Chemistry) - established in 1892

ALKANES (CnH2n+2) ALKYL GROUPS (CnH2n+1)

Alkyl Groups

Alkyl group - derivative of corresponding alkane

The general formula: R = CnH2n+1. R – any alkyl group.

Alkyl group has 1 hydrogen atom less than the corresponding alkane.

IUPAC RULES FOR NAMING ALKANES

1. The name of the compound consist of the name of the longest chain prefixed by the names of attached alkyl groups.

2. Select the longest chain.

3. Consider all alkyl groups attached to it.

4. Number the carbon atoms in the carbon chain starting from the end closest to the first carbon atom that has attached alkyl group.

5. Name each branch-chain alkyl group and designate its position by a number (3-methyl means a methyl group attached to carbon 3)

4. If the same alkyl groups occur more than once, indicate this by prefix (di-, tri-, tetra etc) (dimethyl indicates two methyl groups). The numbers indicating the positions of these alkyl groups are separated by comma, followed by a hyphen, and placed in front of the name (2,3-dimethyl).

5. When several alkyl groups are attached to the parent compound, list them in alphabetical order.





Name the following compound

2-methylbutane


2-methylpentane

Each of the following formulas represent the same compound – 2-methypentane


2,3-dimethylbuthane




4. Name each branch-chain alkyl group and designate its position by a number


Name the following compounds

2,2-dimethylbutane

2,4-dimethylhexane

H3

3-methylhexane


3-chloro- 4-ethyl-2,4-dimethyloctane






5. When several alkyl groups are attached to the parent compound, list them in alphabetical order.

2,2,4-trimethylpentane

2-methylhexane

5-ethyl-3-methyloctane


H3C CH2CH C

CH3

CH3CH

CH3 CH3

CH2

Cl


CH3C CH2CH2CHCH3

CH2CH3CH2CH3

CH3

CH3

CH3CH3

CH3

CH2

CH CH

CH2

3,4-dimethylhexane

3-chloro-2,5,5-trimethylheptane

3,3,6-trimethyloctane

Write the formula for:

CH3CH2

CH CH2 CH3

CH2

CH3

3-ethylpentane

3-bromo-5,6-diethyl-2,7-dimethyl-5-propylnonane

CH3CH CH CH2 C

CH2

CH3

CH CH CH2 CH3

CH2

CH3

CH3 CH3

CH2

CH2

CH3

Br

Reactions of Carbon

1. Oxidation-reduction reactions

Oxidation of carbon compound

Reduction of carbon compound

2. Substitution reactionIf in a reaction one atom in a molecule is exchanged by another atom or group of atoms

3. Elimination reactionIf a single reactant is split into two product, and one of the products is eliminated. Multiple bonds are formed

4. Addition reaction

Two reactants adding together to form a single product. Reverse of an elimination reaction

CH3CH2Cl H2O CH3CH2OH HCl+ +

Categorize each reaction

addition

substitution

elimination

CH3CH2CH2CH3CH3CH CHCH3

H2+

CH2 CH2 H2O CH3CH2OH+

Reactions of alkanes

1. Combustion (with the production of large amount of heat energy)

Mechanical energy Electrical

energy

Combustion reactions are the most important for economics.

Combustion reactions are the most active reactions of alkanes.

In all other reactions alkanes are sluggish and demand activation (high temperature, catalists)

CH4(gas) + O2(gas) CO2(gas) + 2H2O + 191,8 kcalthermal energy

2. Halogenation (a substitution reaction)

A halogen (Cl or Br) is substituted for a hydrogen atom in halogenation reactions.

CH3CH3 + Br2

CH3CH2Br + HBrbromoethane

CH3CH3 + Cl2 CH3CH2Cl + HClchloroethane

Alkylhalides are useful as intermediates for manufacturing of other substances

3. Dehydrogenation (an elimination reactions)Alkanes lose hydrogen during dehydrogenation

4. Cracking

Breaking up large molecules to form smaller ones

C16H34 C8H18 + C8H16

alkane alkane alkene

propane

propeneCH3CH2CH3 CH3CH CH2

+ H2

Alkenes are formed (useful chemical intermediates)

4. Isomerization (rearrangment of molecular structure)

CH3CH2CH2CH2CH3 CH3CH2CHCH3

CH3

catalist

, pressure

Halogenation reaction is used for production of petrochemicals (chemicals derived from petroleum and used for other purposes than fuel)

Dehydrogenation, cracking and isomerization reactions are used for production of motor fuels.

Alkyl halides formation

CH4 + Cl2 CH3Cl + HClchloromethane

Reaction of methane with chlorine gives the mixture of mono-, di-, tri-, and tetrasubstituted chloromethanes

CH4 CH3Cl CH2Cl2 CHCl3 CCl4 + HClCl2 Cl2 Cl2 Cl2

The more chlorine the more CCl4.

chloro- methane

dichloro-methane

trichloro-methane

tetrachloro-methane

Monosubstitution product - one hydrogen atom is substitued by another atomDi-, tri, tetra- and so on substituted compounds – two, three, four hydrogen atom are substitued by another atoms

CYCLOALKANES

Hydrocarbons

Aromatic (contain the benzene ring)

Aliphatic (open-chain and cyclic)


Cycloalkanes Cycloalkenes

Cycloalkanes (cycloparaffins, naphthenes) – cyclic, or close-chain, alkanes. Cycloalkanes are saturated hydrocarbons.General formula – CnH2n (two fewer hydrogen atoms than the corresponding open chain alkane)

Add prefix cyclo to the name of alkane with the same number of carbon atom

Naming of Cycloalkanes

UNSATURATED HYDROCARBONS

UNSATURATED HYDROCARBONS

Widely used: polymers (plastic things); in medicine, cosmetics, perfumes, flavorings; detergents, insecticides, dyes.

Hydrocarbons





Alkenes – double bond Alkynes – triple bond Aromatic – benzene ring

Nomenclature of alkenes

1.Select the longest carbon-carbon chain containing the double bond

2.Name this compound as you would an alkane but change the –ane ending to –ene. Example: propane is changing to propene.

3.Number the carbon chain of compound starting with the end nearer to the double bound.

4.Place the number indicating the location of double bond in front of the alkene name (example: 3-propene)

5.Branch chains and other groups are treated as for alkanes.

1-butene

2-butene

3-methyl-1-butene

3-propyl-1-hexene


Write a structural formula for:

4-methyl-2-pentene

7-methyl-2-octene

IMPORTANT: in naming of alkenes the double bond must be included in the chain even if there is longer chain in this compound

the longest carbon chain contains six carbons

We must include the double bond in the chain

the carbon chain containing the double bond has five carbons

2-ethyl-1-pentene


3-methyl-2-pentene

2,4-dimethyl-2-pentene

2-methyl-1-butene

2-methyl-2-butene


3-methyl-3-heptene

3-methyl-1-heptene

CH3 CH2

CH3

CH2

CHCH2C CH3

CH3 CH2

CH2

CH

CH2CH2CH CH3

CH3 CH2

CH2

CH2

CH

CH2CH2C CH3

CH3

3-ethyl-3-methyl-1-heptene

Write a structural formula for:

4-chloro-5,6-diethyl-2,7-dimethyl-5-propyl-2-nonene

CH3C CH

CH3

CH

Cl

C

CH2

CH2

CH3

CH3

CH2

CH

CH3

CH2

CH

CH3

CH2CH3

4,5-dichloro-2,3-dimethyl-1-pentene

C CH

CH3

CH

Cl

CH2

CH3

CH2

Cl

Nomenclature of alkenes containing more than one double

bondCompounds with two (di) double bounds are called dienes, with three (tri) – trienes.

1,4-pentadiene 2-methyl-1,3-butadiene



C C C

Cl

CH2

CH3

CH

Cl

4,5-dichloro-3-methyl-1,2,4-pentatriene

5-methyl-4-pentyl-2,5-octadieneCH3

CH

CH

CH

CH3

CH2C

CH3

CH

CH2

CH3

CH2CH2

CH2

Geometric Isomerism in Alkenes

1,2-dichloroethane

carbon atoms can rotate freely about the single bond

these two compounds are identical

carbon atom can not rotate about the double bond

Restricted rotation of carbon atom around the bond with other carbon atom results in the phenomenon known as geometric isomerism

these compounds are different

cis-1,2-dichlorethene

trans-1,2-dichlorethene

Geometric isomers (cis-trans isomers) -compounds that differ from each other only in the geometry of their molecules and not in the order of their atoms

Cis- isomer has substituent groups on the same side of the double bond

Trans- isomer has substituent groups on the opposite sides of the double bond

An alkene shows cis-trans isomerism when each carbon atom of the double bond has two different kinds of groups attached to it

cis-isomer

trans-isomer

An alkene doesn’t show cis-trans isomerism if one carbon atom of the double bond has two identical groups attached to it

C CAA

BBC C

A

A B

B

C CH

H

H

HC C

H

H

CH3

H

cis-2-butene trans-2-butene

Write geometric isomers for: 2-butene

CH CH3CH3 CH

Chemical properties of alkenesAddition

So far as alkenes have double bonds they are more reactive than alkanes and undergo addition reactions.

Some of the reagents that can be added to alkenes: hydrogen, halogens, hydrogen halides, water, sulfuric acid, etc.

C

C

Brown color of Br2 disappears in this reaction.

As result of addition alkenes are converted to saturated molecules.

Addition reactions are reverse to the elimination reactions.

Markovnikov’s rule

When an asymmetrical molecule HX (HCl) adds to a carbon-carbon double bond, the hydrogen from HX goes to the carbon atom that has the greater number of hydrogen atoms.

Write the formulas for the organic compounds formed when 2-methyl-1-butene reacts with (a) H2, (b) Cl2, (c) HCl, (d) H2O

2-methyl-1-butene

(a)(b)

1,2-dichloro-2-methylbutane

(c) (d)

Hydrocarbons





Widely used: plastic things; in medicine, cosmetics, perfumes

Alkynes – unsaturated hydrocarbons containing triple bond

Alkynes

Naming of alkynes1. Select the longest carbon-carbon chain containing the

triple bond.

2. Name this compound as for alkene but change the –ene ending to –yne.

3. Number the carbon chain of compound starting with the end nearer to the triple bound.

4. Place the number indicating the location of triple bond in front of the alkyne name (example: 3-propyne)

5. Branch chains and other groups are treated as for alkanes.

Chemical propertiesAddition Reactions

Positive Bayer’s test with potassium permanganate (disappearance of purple-pink color)

Reactions with halogens. Either one or two molecules of halogens can be added.

Reactions with hydrogen halides.

Vinyl chloride is widely used in chemical industry, for example for production of plastic polyvinyl chloride

This reaction follows Markovnikov’s rule.

These reactions follow Markovnikov’s rule.

Acetylene is the most important industrially.

Many different polymers are manufactured from acetylene (production of clothes, superabsorbents (disposable diapers, soil additives))

Aromatic hydrocarbonsStructure

Benzene and its derivatives are classified as aromatic hydrocarbons.

Kekule’s formula:

carbon atoms in a benzene molecule are arranged in a six-membered ring with one hydrogen atom bonded to each carbon atom and with three double carbon-carbon bonds.

Molecular formula of benzene: C6H6

Benzene doesn’t react as a typical alkene (doesn’t decolorize bromine solution, negative Bayer’s test). Benzene behaves chemically like a typical alkane (substitution reactions).

Structure of benzene can be represent by different formulas

Kekule structures

Kekule formulas are classical however such structures actually doesn’t exist

Formulas C or D more accurately represent the real benzene structure

Naming of aromatic compoundsMonosubstituted

benzenes

1.Add the name of a substitutent group as a prefix to the word benzene

2.Write the name as one word

3.Position of substituent is not important

F

CH2CH2CH3

OHCH2CH3

Name the following compounds:

fluorobenzene

propylbenzene

ethylbenzene hydroxybenzene

Some monosubstituted benzenes have special (trivial) names. These names should be memorize.

The group (C6H5) is called phenyl group

The name phenyl can be used to name compounds that can not easily be named as benzene derivatives

3-chloro-2-phenylpentane

diphenylmethane

Disubstituted BenzenesIn disubstituted benzenes the prefixes

ortho-, meta- and para- (o-, m-, p-) are used for naming.

In ortho- disubstituted compounds, the two substituents are located on adjacent carbon atoms

In meta- disubstituted compounds, the two substituents are one carbon apart

In para- disubstituted compounds, the two substituents are located on opposite points of ring

ortho-dichlorobenzene

Name the following compounds:

meta-dichlorobenzene para-dichlorobenzene

CH2CH3

CH2CH3

CH2CH3

CH2CH3

CH2CH3

CH2CH3

ortho-diethylbenzene meta-diethylbenzene

para-diethylbenzene

When the two substituents are different the names of two substituents are given in alphabetical order

o-bromochlorobenzene

m-ethylnitrobenzene

CH2CH3

CH3

CH2CH3

CH2CH2CH2CH3

p-ethylmethylbenzene

o-butylethylbenzene

Sources and using of aromatic hydrocarbons

Sources:

Coal tar (by-product of the manufacture of coke)

Alkanes found in petroleum

Using: in the production of - drugs, - dyes, - detergents, - explosives, - insecticides, - plastics, - synthetic rubber.

ALCOHOLS

Alcohols – a class of compounds containing the hydroxyl (-OH) functional group

General formula – ROH

Alcohols are derived from aliphatic hydrocarbons by the replacement of at least one hydrogen atom with a hydroxyl group

Classification of AlcoholsPrimary – carbon atom to which the –OH group

is attached is directly bonded to one other carbon atom

Secondary – carbon atom to which the –OH group is attached is directly bonded to two other carbon atom

Tertiary – carbon atom to which the –OH group is attached is directly bonded to three other carbon atom

If two or more –OH groups are attached to the same carbon atom such compound is not stable

If two or more –OH groups are attached to the different carbon atoms such compounds is stable

polyhydroxy alcohols

monohydroxy-, dihydroxy-, trihydroxy-, tetrahydroxy-, and so on.

Alcohols can be also classified as

The formulas of alcohol can be written as follow:

or

2-butanol

2-butanol

Naming of alcohols

1.Select the longest chain of carbon atoms containing the hydroxyl groups

2.Number the carbon atoms in this chain so that the one bearing the –OH group has the lowest possible number

3.Form the parent alcohol name by replacing the final –e of alkane by –ol.

4.Locate the position of the –OH by placing the number of corresponding carbon atom before the alcohol name.

5.Name each side chain and designate its position by number

Name the alcohol CH3CH2CH2CH2OH

1. The longest carbon chain has 4 carbons

2. Number the carbon atoms (carbon bonded to –OH must have number 1)

3. Four carbon alkane is called butane. Change –e to –ol butanol

4. OH group is on carbon 1, so place 1 before butanol

Result: 1-butanol


1-propanol

2-propanol cyclohexanol

3-methyl-1-butanol 4-methyl-2-hexanol

2-ethyl-1-pentanol 5-bromo-5-methyl-3-hexanol

CH3 CH2CH2

OH CH3 CH CH3

OH

OH

CH3 CH CH2

CH3

CH2OH CH3CH2CHCH2CHCH3

CH3OH

CH3CH2CHCH2CH2CH3

CH2OHCH3CH2CHCH2CCH3

OH CH3

Br

OH

CH33-methylcyclopentanol

Write the structural formulas for:

3,3-dimethyl-2-hexanol

CH3

CH3

OH

CH3CH C CH2CH2CH3

OH

CH3

Cl

2-chloro-4-methylcyclopentanol

CH2CH2

CH CH3

OH

4-phenyl-2-butanol

OH

ClCl

Cl

2,3,4-trichlorocyclobutanol

Nomenclature of alkohols containing more than one -OH

groupsCompounds with two (di) –OH groups are called diols, with three (tri) – triols.


1,3-cyclohexanediol

1,2-ethanediol

HOCH2 CH2OH

OH

OH

OH OH

CH2CHCH2

OH1,2,3-propanetriol

CH3CH3CH

CH2OH

CHOH CHOH CH

CH2CH3

2,5-dimethyl-1,3,4-heptanetriol

relatively high boiling point (depends on the hydrogen bonding between alcohol molecules)

alcohols containing up to three carbon atom are soluble in water (solubility depends on hydrogen bonding between alcohol molecules and water)

alcohols with 5-11 carbons are oily liquids, 12 or more carbon atoms – waxlike solids

two or more –OH groups increase boiling point and solubility

Alcohols:

Chemical properties of alcohols

Acidic and basis properties (similar to water properties)

a) In acidic solution alcohols accept a proton

oxonium ion (protonated alcohol)

b) Alcohols react with alkali metals to release hydrogen

alkoxide ion (strong base)

1. OxidationThe hydroxyl group gives an alcohol the capability of forming an aldehide, ketone or carboxylic acid

Tertiary alcohols don’t have a hydrogen on the –OH carbon and can not react with oxidizing agents

Oxidation occurs at the carbon atom bonded to the –OH group and this atom becomes an aldehyde or carboxylic acid. The rest of the molecule remains the same.

Oxidation of ethanol in organism (in liver)

Toxic compound, can cause the liver damage (liver

cirrhosis)

Can be used as sourse of energy for the organism

2. Dehydration (elimination of water)

a. Intramolecular dehydration (the alkenes are formed)

Saytzeff’s rule. If there is the choice of positions for double bond the preferred location is the one that gives the more highly substituted alkene – that is, the alkene with the most alkyl groups attached to double-bond carbons.

Remove the hydrogen from the carbon with fewer hydrogen.

b. Intermolecular dehydration (the ethers are formed)

This type of reaction occurs only between primary alcohols.

Such type of reactions is called condensation reaction (two molecules are combined with removing of small molecule).

3. Esterification (convertion of alcohols to esters)Alcohol reacts with carboxylic acid to form an ester and water.

Utility of the Hydroxyl Group

Common AlcoholsMethanol (wood alcohol)

Preparation: - heating of wood to high temperature without oxygen (distructive distillation) - hydrogenation of carbon monoxide under the high pressure

methanol

Physical properties:

highly flammable liquid

poisonous, can cause blindness and death

Using: -convertion to formaldehyde –manufacture of esters and other chemicals –production of denaturing ethyl alcohol -industrial solvent

Ethanol (ethyl alcohol, spirit)Preparation:

-fermentation. Starch is converted to sugar, then sugar is converted to ethanol. The enzymes of yeast are used.

-acid-catalyzed addition of water to ethylene (ethylene can be obtain from petroleum)

Using: -intermediate in the production of other chemicals -solvent for many organic substances -ingredient for pharmaceutical, perfumes, flavorings -ingredient of alcoholic beverages

Glycerol (1,2,3-propanetriol, glycerine)Contains three –OH groups.

Physical properties: -liquid with a sweet, warm taste -hygroscopic (is able to hold water molecules by hydrogen bonding)

Preparation: -by-product of processing fats to make soap and other products -it is synthesized from propene

Using: -manufacturing of polymers -manufacturing of explosives -emollient in cosmetics

ETHERSGeneral formula R-O-R’.

R and R’ can be saturated, unsaturated or aromatic hydrocarbons. R and R’ can be alike or different.

Naming ethers

A. Common names (only for naming simple ethers)

Common names are formed from the names of groups attached to oxygen atom

O

Name the following compounds using common names

diethyl ether; ethyl ether or ether

CH3CH2-O-CH2CH3

diphenyl ether

OCH3

methyl phenyl ether

CH3CH2CH2O CH2CH2CH2CH3

butyl propyl ether

CH3CH2O CHCH3

CH3

ethyl isopropyl ether

OCH2 CH CH CH2

divinyl ether

B. Naming according to IUPAC system

Alkoxy group is named by dropping the ending –yl of the alkyl name and adding the suffix –oxy.

Examples:

CH3O-, alkyl is called methyl, replace ending –yl to –oxy. Group is called methoxy. CH3CH2O- - is called ethoxy (eth + oxy).

- is called phenoxy (phen + oxy).

Group R-O- is called alkoxy group (consist of alkyl group R- and oxygen atom).

Rules for naming ethers

1. Select the longest carbon chain and label it with the name of corresponding alkane.

2. Change the –yl ending of other hydrocarbon group to –oxy.

3. Combine the two names giving the alkoxy name and its position on the longest carbon chain first.

metoxyethane

O

CH3CH2-O-CH2CH3

OCH3

CH3CH2CH2O CH2CH2CH2CH3

CH3CH2O CHCH3

CH3


ethoxyethane

methoxybenzene

phenoxybenzene

1-propoxybutane

CH3CH2CH2O CHCH2CH3

CH3

2-propoxybutane

2-ethoxypropane

CH3

CH3CH2CH2CH2 O CHCH2CH3

CH2

3-butoxypentane


O CH2CHCH3CH3

CH3

1-methoxy-2-methylpropane

OCH3

Clm-chloromethoxybenzene

OCH2CH2CH3

ClCl

1,2-dichloro-4-propoxybenzene

CH3CH

CH3

O CHCH2CHCH3

CH3 CH3

2-isopropoxy-4-

methylpentane

Physical Properties of EthersThe shape of molecule is similar to water and alcohol molecules

Ethers are more polar than alkanes (alkanes don’t conatain oxygen atom) Ethers are less polar than alcohols or water (ethers don’t contain hydrogen)

Ethers form hydrogen bonds with water molecules or acids

Ethers – very good solvents for organic compounds

Some polar compounds (water, alcohols) can be dissolve to some extent in ethers

Ethers are highly flammable

Vapors can form with air explosive mixture

Ethers with long carbon chain are insoluble in water

Ethers with small carbon chain are very little soluble in water and acids

Solubility and boiling point of ethers depend on the carbon chain structure

Ethers have little chemical reactivity

Ethers can slowly react with oxygen from air to form peroxides (explosive substances).

Chemical Properties

Preparation of ethers

1. Intermolecular dehydration of alcohols

2. Williamson synthesis. Alkyl halides react with sodium alkoxides or sodium phenoxides to form ethers. This is the substitution reaction.

ThiolsThiols (mercaptants) – organic compounds containing –SH group.

Naming of thiols

The principle of naming is as for alcohols but except the ending –ol the ending –thiol is used.

CH3SH CH3CH2CHCH3

SHmethanethiol

2-butanethiol

CH3

CH3CH2CHCHCH2CH3

SH

4-methyl-3-hexanethiolSH

cyclohexanethiol

Properties

1. Foul odours (natural gas is odorized by methanethiol to be detectable)

2. Oxidation to disulfides

FunctionsDisulfide structures in proteins. Constituent of coenzyme A (metabolism).

ALDEHYDES AND KETONESALDEHYDES AND KETONES

Structure of aldehydes and ketones

C OBoth aldehydes and ketones contain carbonyl group

Differerence: -aldehydes contain hydrogen atom bounded to carbonyl group -ketones have only alkyl or aromatic groups attached to carbonyl group

Methanal is the smallest aldehyde (the first member from the homologous series)

Ethanal is the second member of the homologous series

methyl group on 4 carbon

the longest chain is hexane

4-methylhexanal


OCH3CH2CH2CH2C

Hpentanal

OCH2ClCHCH2CH2C

H

CH3

5-chloro-4-methylpentanal

O

HCCH2CHCH2CHCH3

OH OH

3,5-dihydroxyhexanal

O

HCH CHC

3-phenyl-2-propenal

O

CH3

HCHCHC

CH2CH3

2-methyl-3-phenylpentanal

Naming of Ketones

1.Select the longest chain containing the ketone group.

2.Drop the ending –e from the corresponding alkane name and add the suffix –one.

3.If the chain is longer than four carbons, it is numbered so that the carbonyl group has the lowest number possible. This number is prefixed to the parent name of the ketone.

4.Name other groups attached to parent chain as usual.


CH3 C CH3

O

CH3 C CH3

O

CH2 CH3 C CH3

O

CH2 CH2

propanone

butanone

2-pentanone

CH3 C CH3

O

CH CH2CH2

CH3

4-methyl-3-hexenone

CH3

CH3

CHCH

C O

CH3

OH4-hydroxy-3-methyl-2-pentanone

O

cyclohexanone

O

CH3

CH3

CH32,4,6-trimethylcyclohexanone

CH2 CH2 CCH2CH2OH

O

1-hydroxy-5-phenyl- 2-pentanone

Alternative Names of KetonesIt is used to name simple ketones.List the names of the alkyl or aromatic groups attached to carbonyl carbon together with the word ketone.

methyl ethyl ketone (butanone)

methyl methyl ketone (propanone)

Propanone and butanone are the most widely used ketones. They have the special (common) names: acetone (propanone) and MEK (butanone).


C

O

CH3CH2CH2CH3

ethyl ethyl ketone (diethyl ketone) CH3

CH3

C

O

CH3CH2CH

ethyl isopropyl ketone

C

O

dicyclohexyl ketone

CH3

C

O

CHCH

CH3

CH3

CH3

diisopropyl ketone

Naming of Aromatic KetonesAromatic ketones are named similarly to the aliphatic ketones and can have the special names as well.

C

O

CH3

1-phenylethanone (methyl phenyl ketone)

C

O

CH3CH2

1-phenyl-1-propanone (ethyl phenyl ketone)

2-methyl-1-phenyl-1-butanone

C

O

CH3CH2CH

CH3

Cinnamaldehyde (oil of cinamon)

Benzaldehyde (oil of bitter almonds)

Naturally occurring aldehydes and ketonesMany aldehydes have a specific odour and can be used in flavoring and perfumes

Carvone (chief component of spearmint oil)

Muscone (gland of male musk deer, used in perfumes)

Civetone (secretion of the civet cat, used in perfumes)

Camphor (from the camphor tree)

Cortisone (hormone; produced by epinephrine glands; regulate metabolism in organism; widely used in medicine)

Glucose Ribose Fructose

Sugars; energetic and plastic material for organism

Citral (oil of lemon)

Vitamin K (antihemorrhagic vitamin)

Chemical Properties of Aldehydes and Ketones

C OChemical properties of aldehydes and ketones are determined by the functional carbonyl group

1. OxidationsAldehydes are oxidized to carboxylic acids by different agents (K2Cr2O7+H2SO4; Ag+; Cu2+; oxygen of air)

Ketones are not oxidized by such agents. Ketones can be oxidized under drastic conditions (hot potassium permanganate). Carbon-carbon bonds are broken under these conditions and variety of products are formed.

orange green

The Tollens test (silver-mirror test)Silver ions oxidizes ammonia (Tollens’ reagent is

formed) Ag+ ions are reduced to metallic silver by aldehydes

Add into tube aldehyde, silver nitrate and ammonia

The silver mirror appears on the inner wall of the tube

CH3 C

O

H Ag(NH3)2OH AgCH3 C

O

ONH4 NH3+ + + +2 2 H2O

Tollens’ Reagent

3

Fehling testFehling solutions contain Cu2+ ions in alkaline medium. Cu2+ has blue color. During reaction it is reduced and brick-red copper oxide is formed.

Before reaction (blue color of Cu2+)

After reaction (brick-red color of Cu2O)

Ketones don’t give a positive Tollens or Fehling tests

Tollens or Fehling test can be used to distinguish between aldehydes and ketones

2. Reduction

Aldehydes and ketones are reduced to alcoholsReducing agents: -hydrogen (catalyst Ni); -litium aluminium hydride (LiAlH4); -sodium borohydride (NaBH4).Aldehydes yield primary alcohols; ketones yield secondary alcohols

Common Aldehydes and KetonesFormaldehyde

(methanal)Can be obtained in the oxidation of methanol by oxygen (silver or copper are catalysts)

Properties: -gas -poisonous -very irritating (ingestion can cause death) -soluble in water -37 % solution of formaldehyde is called formalin

Using:

manufacture of polymers;

preservation of biological specimens

Acetaldehyde (ethanal)

Can be obtained in the oxidation of ethanol

Volatile liquid with pungent odorUsing: intermediate in the production of other chemicals (for example, acetic acid)

Three or four molecules of ethanal can polymeraze to form cyclic compounds paraldehyde and metaldehyde, which can be used for production of sedative drugs and pesticides

Acetone (methyl methyl ketone) and MEK (methyl ethyl ketone)

Using: solvents, manufacturing of drugs, chemicals, explosives, in plastic industry; for removal of paints

Acetone and MEK can be obtained by oxidation of secondary alcohols:

Acetone is formed in human body In some diseases (diabetes mellitus, starvation) the concentration of acetone is increased in blood and urine.

INTRODUCTION TO ORGANIC CHEMISTRY; SATURATED HYDROCARBONS.

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Transcript of INTRODUCTION TO ORGANIC CHEMISTRY; SATURATED HYDROCARBONS.