Chapter 22 Families of Organic Compounds. Tetrahedral Carbon Compounds. In tetrahedral compounds the atom or group of atoms responsible for the characteristic.

Chapter 22

Families of Organic Compounds

Tetrahedral Carbon Compounds.

• In tetrahedral compounds the atom or group of atoms responsible for the characteristic properties of the compound is attached to a tetrahedral carbon atom.– Chloroalkanes– Alkanes– Alcohols

Chloroalkanes

Chloroalkanes-One or more of the H atoms in the alkane replaced by a Cl atom.

-Synthesised in the Lab

-Used as solvents

-Not soluble in water(no polarity).

-Dissolve in non-polar solvents like cyclohexane.

STRUCTURAL ISOMERISM IN HALOGENOALKANESSTRUCTURAL ISOMERISM IN HALOGENOALKANES

Different structures are possible due to...

Different positions for the halogen and branching of the carbon chain

2-chlorobutane

2-chloro-2-methylpropane

1-chlorobutane

1-chloro-2-methylpropane

Chloroalkanes

Chloroalkanes

• One or more of the hydrogen atoms in an alkane molecule has been replaced by a chlorine atom, e.g.

• Chloromethane - CH3Cl

• Dichloromethane - CH2Cl2

• Trichloromethane - CHCl3

• Tetrachloromethane - CCl4

Chloromethane

Dichloromethane

Trichloromethane

Tetrachloromethane

Chloroethane

1,1-dichloroethane

1,2-dichloroethane

Naming chloroalkanes

• Last part of name comes from base alkane on which the molecule is built, e.g. chloroethane [2 carbons]

• Number of chlorine atoms indicated by prefix mono, di, tri, tetra etc. in front of chloromethane, e.g. trichloromethane

• Position of each chlorine atom given by a number before the name, e.g.

1,2,2-trichloropropane

1,2,2-trichloropropane

Physical properties

• Physical state: Liquid, except for chloromethane and chloroethane, which are gases at room temperature

• Boiling points higher than the corresponding alkanes, due to polar C-Cl bond(s)

Physical properties

• Not soluble in water

• Soluble in non-polar solvents such as cyclohexane

Uses of chloroalkanes

• Because of their lack of polarity, they are useful solvents, e.g. for

• removing grease and oil from machinery

• removing oil etc. from clothes - dry cleaning

Alcohols• Alcohol’s form a homologous series of compounds.

• The -OH group called the hydroxyl group is the functional group of the alcohols.

Alcohols

Alcohols

• Methanol CH3OH

• Ethanol C2H5OH

• Propan-1-ol C3H7OH

• Propan-2-ol C3H7OH

• Butan-1-ol C4H9OH

• Butan-2-ol C4H9OH

Methanol CH3OH

Ethanol C2H5OH

Propan-1-ol C3H7OH

Butan-1-ol C4H9OH

Propan-2-ol CH3CH(OH)CH3

Butan-2-ol CH3CH(OH)C3H7

Classification of alcohols

1. Primary alcohol: contains one carbon atom directly attached to the carbon that contains the hydroxyl group, e.g. propan-1-ol

2. Secondary alcohol: contains two carbon atoms directly attached to the carbon that contains the hydroxyl group, e.g. propan-2-ol

Physical properties

• Physical state: Liquid

• Boiling points much higher than the corresponding alkanes, due to polar OH group

Physical properties

Solubility of methanol in • (i) cyclohexane – not very soluble

methanol is polar cyclohexane is not • (ii) water - completely soluble

because it is polar.• As alcohol molecule gets bigger the polar

part becomes less significant so the alcohol becomes less soluble in water and more soluble in cyclohexane

Butan-1-ol is

–(i) soluble in cyclohexane

–(ii) not very soluble in water

• The polar OH group is becoming less significant as the molecule gets bigger

Comparison with water

• Both have polar OH groups

• Alcohols have a non-polar part

• Both form hydrogen bonds between their molecules

• Water is more polar and has a greater capacity to form hydrogen bonds and so has a higher boiling point than methanol or ethanol

Methanol

• Methanol: is toxic (can cause blindness, insanity and death)

• It is added to industrial alcohol to prevent people drinking it. This mixture is called methylated spirits.

• The methanol acts as a denaturing agent – it renders a substance unfit for purpose without destroying the usefulness or applications of the substance. A purple dye is often added as a warning.

Ethanol

• Ethanol: is produced by fermentation. Fruits provide the sugar and yeast may need to be added.

• The enzyme zymase in yeast catalyses the reaction.

C6H12O6 2C2H5OH + 2CO2

Alcoholic Drinks

Ingredient

Drink % (v/v) alcohol

Grapes Wine 12

Apples Cider 4.5

Malted grain

Beer 5

Ethanol

• To produce drinks of higher alcohol concentration the fermented liquids must be distilled.

• Spirits (whiskey, brandy, gin, vodka) contain 40% alcohol.

Gasohol

• Ethanol obtained from sugar cane is used for making gasohol in Brazil. This is then used as a fuel.

Uses of ethanol

1. Alcoholic drinks

2. Fuel

3. Solvent (can dissolve both polar and non-

polar solutes)

Primary Secondary and Tertiary

• Primary Alcohol -one C attached to the C which has the –OH group.

• Secondary Alcohol -Two C attached to the C which has the –OH group.

• Tertiary Alcohol -Three C attached to the C which has the –OH group.

Examples of Alcohol’sMethanol-added to industrial alcohol to

prevent consumption.

Ethanol-Used in alcoholic drinks, as a fuel and as a solvent.

Ethanol is produced by fermentation. Yeast

C6H12O6 --------> 2C2H5OH + 2CO2

Zymase

Physical Properties of Alcohol’sBoiling points

Alcohol’s have a higher boiling point than corresponding alkanes. This is due to Hydrogen bonding between the Alcohol molecules.

Hydrogen bonding between alcohol molecules

Solubility of Alcohols

Hydrogen bonding also results in Alcohol’s been soluble in water.(C1-C3)

This solubility decreases as the length of the Carbon chain increases. This is due to the polar -OH group(which is responsible for solubility) been counteracted by the larger insoluble alkyl group

Planar Carbon Compounds.

Alkenes Alkynes

Aldehydes Ketones

Carboxylic Acids Esters

Aromatic CompoundsNote.

These compounds have double bonds

AldehydesAn aldehyde is a compound containing a carbonyl

group with at least one hydrogen attached to it.

• Functional Group –CHO (Carbonyl group)• Strongly Polar

Formal names for aldehydes include the prefix from the alkyl group and the suffix -al.

Two of the simplest aldehydes are

Aromatic aldehydes include oil of almonds, vanillin, and oil of cinnamon.

Aldehydes

Aldehydes

• Methanal HCHO

• Ethanal CH3CHO

• Propanal C2H5CHO

• Butanal C3H7CHO

Methanal

Ethanal

Propanal

Butanal

Physical properties

• Physical state: Liquid, except methanal, which is a gas at room temperature

• Boiling points higher than the corresponding alkanes, due to polar +C = O- group, but lower than the corresponding alcohols

Physical properties

• Short chain aldehydes are soluble in water due to the polar carbonyl group

• As the number of carbon atoms in a molecule of the ester increases, solubility in water decreases, while solubility in cyclohexane increases

Benzaldehyde

• Aromatic aldehyde• Found in almond

kernels

Boiling points and solubility of the aldehydes

Boiling points

Not possible to form Hydrogen Bonds between the aldehyde molecules. There is however Dipole-Dipole bonds between the aldehyde molecules.

This results in the aldehydes having boiling point higher than corresponding alkanes but lower than corresponding alcohol.

Eg Ethanal Bp = 21C Ethanol Bp = 78C

Compare Boiling PointsMolecule Type Boiling point (°C)

CH3CH2CH3 alkane -42

CH3CHO aldehyde +21

CH3CH2OH alcohol +78

Notice that the aldehyde (with dipole-dipole attractions as well as dispersion forces) has a boiling point higher than the similarly sized alkane which only has dispersion forces.However, the aldehyde's boiling point isn't as high as the alcohol's. In the alcohol, there is hydrogen bonding as well as the other two kinds of intermolecular attraction.Although the aldehydes and ketones are highly polar molecules, they don't have any hydrogen atoms attached directly to the oxygen, and so they can't hydrogen bond with each other.

• Methanal- only aldehyde that is a gas at room Temperature.(also called Formaldehyde)

• Lower members of the aldehyde’s are soluble in H20 and like the alcohol’s will dissolve in both polar and non-polar substances. This is due to H bonding between the O atom in the carbonyl and the H atom of the water molecule.

• Like the alcohol’s, the solubility in water decreases with the length of the carbon chain.

Ketones• Functional group R-CO –R

• Physical properties similar to the Aldehydes due to the Dipole-Dipole forces between the Ketone molecules.

• Solubility similar to the Aldehydes.

• Since Propanone(acetone) and Butanone can act as solvents in both polar and non polar solvents they are widely used in industry

In ketones, the carbonyl group has two hydrocarbon groups attached.

Notice that ketones never have a hydrogen atom attached to the carbonyl group. Propanone is normally written CH3COCH3. Notice the need for

numbering in the longer ketones. In pentanone, the carbonyl group could be in the middle of the chain or next to the end - giving either pentan-3-one or pentan-2-one.

Ketones

Ketones

• Propanone CH3COCH3

• Butanone C2H5COCH3

Propanone

Butanone

Physical properties• Physical state: Butanone and propanone are

liquids at room temperature

• Boiling points higher than the corresponding alkanes, due to polar +C = O- group, but lower than the corresponding alcohols

• Short chain ketones such as propanone are soluble in water due to the polar carbonyl group

• Ketones are soluble in non-polar solvents such as cyclohexane

Uses of propanone

• Propanone is used as a solvent (e.g. In nail varnish remover)

Carboxylic acids

Carboxylic Acids.

Functional Group R- COOH

Examples of Carboxylic AcidsMethanoic Acid HCOOH

Ethanoic Acid CH3COOH

Propanoic Acid C2H5COOH

Carboxylic acids

• Methanoic acid HCOOH

• Ethanoic acid CH3COOH

• Propanoic acid C2H5COOH

• Butanoic acid C3H7COOH

Methanoic acid HCOOH

Ethanoic acid CH3COOH

Propanoic acid C2H5COOH

Butanoic acid C3H7COOH

Physical properties

• Physical state: Methanoic acid and ethanoic acid are liquids, while propanoic acid and butanoic acid are solids

• Short chain carboxylic acids are soluble in water due to the polar COOH group

• Carboxylic acids are soluble in non-polar solvents such as cyclohexane

Boiling points of carboxylic acids

• Boiling points higher than the corresponding alcohols

• This is because carboxylic acids form dimers, where two carboxylic acid molecules are held together by two hydrogen bonds

• This is possible due to polarity in both the C=O and O-H bonds in each carboxylic acid molecule

Ethanoic acid dimer

δ+

δ+

δ+

δ-

δ-

δ-

δ-

δ+

Occurrence and uses

• Methanoic acid is found in the sting of ants and nettles

• Ethanoic acid is the principal acid in vinegar• Ethanoic acid is used in the manufacture of

cellulose acetate• Propanoic acid, benzoic acid and their salts

(e.g. sodium benzoate) are used as food preservatives

Examples of Carboxylic acid and uses

• Methanoic acid(formic acid) sting of nettles and ants

• Ethanoic acid(acetic acid)-vinegar,Cellulose acetate used in varnishes,laquers, photographic film, rayon

• Propanoic acid, Benzoic acid-Preservatives

• Butanoic acid- smell of rancid butter,smelly socks

Examples of carboxylic acids

The name counts the total number of carbon atoms in the longest chain - including the one in the -COOH group. If you have side groups attached to the chain, notice that you always count from the carbon atom in the -COOH group as being number 1

Solubility and Boiling PointsBoiling pointsEthanoic Acid Higher Bp/Mp than

corrisponding Alcohol.Why?

This is due to the effects of Hydrogen

Bonding.

In pure acid the molecules

group together to form clusters of

dimers(two molecules) held together by

2 Hydrogen Bonds.

Solubility

Soluble in Water due to their ability to form Hydrogen bonds with water.This solubility decreases with increasing length of the carbon chain.

Esters

Esters

Esters are formed by the reaction of a carboxylic acid with an alcohol e.g.

CH3COOH + CH3OH = CH3COOCH3 + H2O

Ethanoic acid Methanol Methyl ethanoate

Naming esters: methyl ethanoate

• The first part of the ester name comes from the parent alcohol with the - anol changed to – yl and the second part of the name comes from the parent acid with the - oic acid changed to – oate.

Methyl methanoate HCOOCH3

Ethyl methanoate HCOOC2H5

Methyl ethanoate CH3COOCH3

Ethyl ethanoate CH3COOC2H5

Physical properties

• Physical state: Liquid

• Boiling points higher than the corresponding alkanes, but lower than the corresponding alcohols

Physical properties

• Soluble in water and non-polar solvents such as cyclohexane

• As the number of carbon atoms in a molecule of the ester increases, solubility in water decreases, while solubility in cyclohexane increases

Occurrence and uses of esters

• Occur naturally in fruits – are responsible for their flavours -

• and flowers – are responsible for their pleasant smells

• Fats and oils are naturally occurring esters of long chain carboxylic acids

• Ethyl ethanoate is used as a solvent for printing inks and paints

Esters.Functional Group R-COO-R

Alcohol + Carboxylic Acid Ester + Water

This reaction is called a condensation reaction since it results in the loss of a water molecule

Lower members of the Ester family are volatile liquids with Fruity smell.

-Low Bp because H bonds are not formed with each other.

-Polar molecules that can form H bonds with Water.

Lower members(up to C-5) are fairly soluble in water

Polyester-millions of ester molecules linked together

Solid ester = Fat

Liquid Ester = Oil

Aromatic compounds

• Aromatic compounds contain a Benzene ring.

• Benzene itself is carcinogenic though many aromatic compounds are not dangerous.

• Form basis of many pharmaceutical compounds, dyes detergents, herbicides, disinfectants e.t.c.

STRUCTURE OF BENZENE - STRUCTURE OF BENZENE - DELOCALISATIONDELOCALISATION

The theory suggested that instead of three localised (in one position) double bonds, the six p () electrons making up those bonds were delocalised (not in any oneparticular position) around the ring by overlapping the p orbitals. There would be nodouble bonds and all bond lengths would be equal. It also gave a planar structure.

6 single bonds

STRUCTURE OF BENZENE - STRUCTURE OF BENZENE - DELOCALISATIONDELOCALISATION

6 single bonds one way to overlapadjacent p orbitals

The theory suggested that instead of three localised (in one position) double bonds, the six p () electrons making up those bonds were delocalised (not in any oneparticular position) around the ring by overlapping the p orbitals. There would be nodouble bonds and all bond lengths would be equal. It also gave a planar structure.

STRUCTURE OF BENZENE - STRUCTURE OF BENZENE - DELOCALISATIONDELOCALISATION

6 single bonds one way to overlapadjacent p orbitals

anotherpossibility

The theory suggested that instead of three localised (in one position) double bonds, the six p () electrons making up those bonds were delocalised (not in any oneparticular position) around the ring by overlapping the p orbitals. There would be nodouble bonds and all bond lengths would be equal. It also gave a planar structure.

STRUCTURE OF BENZENE - STRUCTURE OF BENZENE - DELOCALISATIONDELOCALISATION

6 single bonds one way to overlapadjacent p orbitals

delocalised piorbital system

anotherpossibility

The theory suggested that instead of three localised (in one position) double bonds, the six p () electrons making up those bonds were delocalised (not in any oneparticular position) around the ring by overlapping the p orbitals. There would be nodouble bonds and all bond lengths would be equal. It also gave a planar structure.

STRUCTURE OF BENZENE - STRUCTURE OF BENZENE - DELOCALISATIONDELOCALISATION

6 single bonds one way to overlapadjacent p orbitals

delocalised piorbital system

anotherpossibility

This final structure was particularly stable andresisted attempts to break it down through normalelectrophilic addition. However, substitution of anyhydrogen atoms would not affect the delocalisation.

The theory suggested that instead of three localised (in one position) double bonds, the six p () electrons making up those bonds were delocalised (not in any oneparticular position) around the ring by overlapping the p orbitals. There would be nodouble bonds and all bond lengths would be equal. It also gave a planar structure.

STRUCTURE OF BENZENESTRUCTURE OF BENZENE

STRUCTURE OF BENZENESTRUCTURE OF BENZENE

ANIMATIONANIMATION

The animation doesn’t work on early versions of Powerpoint

WHY ELECTROPHILIC ATTACK?WHY ELECTROPHILIC ATTACK?

Theory The high electron density of the ring makes it open to attack by electrophiles

HOWEVER...

Because the mechanism involves an initial disruption to the ringelectrophiles will have to be more powerful than those which reactwith alkenes.

A fully delocalised ring is stable so will resist attack.

Aromatic compounds

Aromatic compounds

• Aromatic compounds are compounds which contain a benzene ring in their molecules

Aromatic hydrocarbons

• Benzene C6H6

• Methylbenzene C7H8

• Ethylbenzene C8H10

Benzene

Benzene molecule

• The six carbon-carbon bonds in benzene are identical, intermediate in length between double and single bonds

Sigma bonding in benzene

• Six carbon atoms joined to form a hexagonal planar ring.

• Each carbon has four valence electrons

• One of these is used to form a bond with a hydrogen atom.

• Two other electrons are used to form sigma bonds with the carbon atoms on either side.

What the circle means

• The 6 valence electrons not involved in sigma bonding are shared between the six carbon atoms in the molecule

• not localised into 3 double bonds

• For convenience the C and H atoms are not shown

• Ring in centre indicates a delocalised pi bond

Methylbenzene

Ethylbenzene

Physical properties

• Physical state: Benzene. methylbenzene and ethylbenzene are liquids

• Insoluble in water

• Soluble in non-polar solvents such as cyclohexane

Uses

• Methylbenzene is used as an industrial solvent

Range and scope of aromatic chemistry

• Pharmaceutical compounds, e.g. Morphine

• Herbicides, e.g. Diuron

• Detergents, e.g. Sodium dodecylbenzenesulfonate

• Dyes, e.g. Martius Yellow

Aromatic acid-base indicators

• The acid-base indicators phenolphthalein and methyl orange are also aromatic compounds

Phenolphthalein Methyl orange

Aromatic compounds and cancer

• Some aromatic compounds are carcinogenic, e.g. Benzene

• However, not all aromatic compounds are carcinogenic; aspirin is an example

Organic Compounds

• Many organic compounds are found free in nature.

• Examples– Benzaldehyde(Almonds)

– Caffeine(coffee)

– Nicotine(cigarettes)

– Pharmaceutical compounds(Aspirin, Iboprofen, Morphine, Paracetamol, Penicillin)

– Food Flavouring(Vanilla)

– insecticides(DDT, Diuron, Naphthalene)

Steam Distillation

• A technique called steam distillation is used to separate oils from plants.

• It involves carrying out distillation in a current of steam . The main purpose is to avoid too high a temperature during distillation as a high temperature may destroy the plant material.

• It is found that the mixture of steam and oil distils below the boiling point of water and well below the boiling point of the oil in the plant.

• The mixture of oil and steam is then passed through a Liebeg condenser and allowed to stand. The oil floats to the top.

Apparatus for steam distillation

Field of Lavender

Emulsion• An emulsion is where the oil droplets are dispersed

throughout the water.

• An organic solvent must be added that dissolves the oil(e.g. cyclohexane) but does not mix with the water. This is then separated and the solvent allowed to evaporate. This process is called solvent extraction.

– Experiment: To extract clove oil from cloves by steam distillation

– See Page 357(book)