Introduction Special nature of carbon Classification of Organic Chemistry Homologous Series &...

Introduction Special nature of carbon Classification of Organic Chemistry Homologous Series & General

Characteristics Separation of Petroleum & Cracking Types of formula Isomerism I.U.P.A.C Nomenclature Compounds of different functional groups

Organic chemistry is the study of carbon compounds. There are around 6 millions compounds of C already known.

Not all C-compounds are organic CO, CO2 considered inorganic Organic compounds covalently bonded

compounds containing carbon, excluding carbonates and oxides

Carbon can join with other carbon atoms to formLong chain carbon atomsBranch chain carbon atomsRings of carbonsMultiple bonds between carbon atoms and atoms of other elements

Why is it possible for carbon to do so?

SPECIAL NATURE OF CARBON - SPECIAL NATURE OF CARBON - CATENATIONCATENATION

CATENATION is the ability to form bonds between atoms of the same element. Carbon forms chains and rings, with single, double and triple covalent bonds, because it is able to FORM STRONG COVALENT BONDS WITH OTHER CARBON ATOMS

Carbon forms a vast number of carbon compounds because of the strength of the C-C covalent bond. Other Group IV elements can do it but their chemistry is limited due to the weaker bond strength.

BOND ATOMIC RADIUS BOND ENTHALPY

C-C 0.077 nm +348 kJmol-1

Si-Si 0.117 nm +176 kJmol-1

The larger the atoms, the weaker the bond. Shielding due to filled inner orbitals and greater distance from the nucleus means that the shared electron pair is held less strongly.

CHAINS AND RINGS

CARBON ATOMS CAN BE ARRANGED IN

STRAIGHT CHAINS

BRANCHED CHAINS

and RINGS

THE SPECIAL NATURE OF CARBONTHE SPECIAL NATURE OF CARBON

You can also get a combination of rings and chains

MULTIPLE BONDING AND SUBSTITUENTS

CARBON-CARBON COVALENT BONDS CAN BE SINGLE, DOUBLE OR TRIPLE



CARBON-CARBON COVALENT BONDS CAN BE SINGLE, DOUBLE OR TRIPLE

DIFFERENT ATOMS / GROUPS OF ATOMS CAN BE PLACED ON THE CARBONS

The basic atom is HYDROGEN but groups containing OXYGEN, NITROGEN, HALOGENS and SULPHURSULPHUR are very common.

CARBON SKELETON FUNCTIONAL CARBON SKELETON FUNCTIONAL GROUP GROUP

The chemistry of an organic compound is determined by its FUNCTIONAL GROUP



ATOMS/GROUPS CAN BE PLACED IN DIFFERENT POSITIONS ON A CARBON SKELETON


THE C=C DOUBLE BOND IS IN A DIFFERENT POSITION

THE CHLORINE ATOM IS IN A DIFFERENT POSITION

PENT-1-ENE PENT-2-ENE

1-CHLOROBUTANE 2-CHLOROBUTANE

Hydrocarbons : Compounds containing carbon and hydrogen only

Non-hydrocarbons : Compounds that may also contain other elements such as nitrogen, sulphur, halogen or oxygen atoms besides hydrogen and carbon.

A series of compounds with the same general formula (e.g. Alkanes CnH2n+2) and functional group (e.g. C=C, OH)

Each member differs from the next by CH2

Members have the same chemical properties.

Members show a gradation in physical properties.

Homologous Series

Condensed structural formula

Structure of Functional Group

Alkanes -CH2CH2-

Alkenes-CH=CH-

C = C

Halogenoalkanes

-X ( X = F, Cl, Br, I)

Alcohols -OH O H

Aldehydes -CHO O C H

Ketones-CO- R

C=O R’

Carboxylic acids-COOH O

C O H

alcoholalcohol

alkenealkene

carboxylic acidcarboxylic acid

ketoneketone

CCH

C

OCH

OH

O

C

C

O

OHO

esterester

carboxylic acid

ether

nitrile

aldehyde

amine

CHCH2

CO OH

OCH

CH2C

N

NH2

C

O

OCH2

CO

H

ester

Page 425

bonding and shape type and strength of intermolecular

forces physical properties nomenclature chemical reactivity

Homologous Series

Polarity Intermoecular forces

Boiling point Solubility in water

Alkane non-polar van der Waals’

low Insoluble

Alkene non-polar van der Waals’

Insoluble

Alcohol Lower members soluble; H bonding to water

Aldehydes/ketones

Dipole-dipole > alkane< alcohol

Lower members soluble; polar and water can H bond with them.

Carboxylic acid Hydrogen bonding

High> alcohol (more H bonding)

Lower members soluble; H bonding to water

Halogenoalkane For same no. of C atoms, I > Br > ClVan der Waals’ forces stronger if Mris higher

Insoluble

Structural Isomers are 2 or more compounds with the same molecular formula but different structural formula.

Example : Isomers of butane

1st isomer 2nd isomer

Condensed CH3CH2CH2CH3 CH3CH(CH3)CH3

formula (has a branched chain)

Pentane has 3 isomers: 1st isomer 2nd isomer 3rd

isomer

Condensedformula

-OH attached to C-1

- OH attached to C-2

- OH attached to C-3

Many more isomers of alcohol.Some are not alcohol. E.g. ether containing C-O-C as a fn’al group.CH3CH2CH2OCH2CH2CH3

Page 428 Practice Qns

1. First 4 members are gases at room temperature & pressure (r.t.p.)

2. All members are insoluble in water but soluble in organic solvent.

Reasons:1. Made up of covalent molecules held by

weak intermolecular forces, so less energy is required to overcome the forces to separate the molecules.

2. Like dissolve like

Do you expect isomers to have similarphysical properties?

Isomers have different physical properties e.g. boiling point or melting point because the different structures will affect the physical properties.

Isomers have the same chemical properties because there are the same number and kind of atoms in each isomer.

I.U.P.A.C. NOMENCLATUREI.U.P.A.C. NOMENCLATURE

A systematic name has two main parts.

STEM number of carbon atoms in longest chain bearing the functional group +a prefix showing the position and identity of any side-chain substituents.

Apart from the first four, which have trivial names, the number of carbons atoms is indicated by a prefix derived from the Greek numbering system.

The list of alkanes demonstrate the use of prefixes.

The ending -ane is the same as they are all alkanes.

Prefix C atoms Alkane

meth- 1 methaneeth- 2 ethaneprop- 3 propanebut- 4 butanepent- 5 pentanehex- 6 hexanehept- 7 heptaneoct- 8 octanenon- 9 nonanedec- 10 decane

Working out which is the longest chain can pose a problem with larger molecules.

CH2CH3 CH2 CH2 CH3CH2 CH2CH2

CH3

CH3

CH3

CH2 CH2CH2

CH3

CH2CH2

CH2CH3 CH3


How long is a chain?

Because organic molecules are three dimensional and paper is two dimensional it can be confusing when comparing molecules. This is because...

1. it is too complicated to draw molecules with the correct bond angles

2. single covalent bonds are free to rotate

All the following written structures are of the same molecule - PENTANE C5H12

A simple way to check is to run a finger along the chain and see how many carbon atoms can be covered without reversing direction or taking the finger off the page. In all the above there are... FIVE CARBON ATOMS IN A LINE.

CH2CH3 CH2 CH2 CH CH3

CH3

CH2CH3 CH3CH

CH2

CH3


How long is the longest chain?

Look at the structures and work out how many carbon atoms are in the longest chain.

CH3

CH3CH

CH2

CH2CH3 CH

CH3

THE ANSWERS AREON THE NEXT SLIDE


CH3

CH2CH3 CH3CH

CH2

CH3


How long is the longest chain?

Look at the structures and work out how many carbon atoms are in the longest chain.

CH3

CH3CH

CH2

CH2CH3 CH

CH3

LONGEST CHAIN = 5

LONGEST CHAIN = 6

LONGEST CHAIN = 6


SUBSTITUENTS Many compounds have substituents (additional atoms, or groups)attached to the chain. Their position is numbered.

A systematic name has two main parts.

SUFFIX An ending that tells you which functional group is present

See if any functional groups are present. Add relevant ending to the basic stem.

In many cases the position of the functional group must be given to avoid any ambiguity

Functional group Suffix

ALKANE - ANEALKENE - ENEALKYNE - YNEALCOHOL - OLALDEHYDE - ALKETONE - ONEACID - OIC ACID

1-CHLOROBUTANE 2-CHLOROBUTANE

SIDE-CHAIN carbon based substituents are named before the chain name. they have the prefix -yl added to the basic stem (e.g. CH3 is methyl).

Number the principal chain from one end to give the lowest numbers.

Side-chain names appear in alphabetical order butyl, ethyl, methyl, propyl

Each side-chain is given its own number.

If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa

Numbers are separated from names by a HYPHEN e.g. 2-methylheptane

Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane

Alkyl radicals methyl CH3 - CH3

ethyl CH3- CH2- C2H5

propyl CH3- CH2- CH2- C3H7


SIDE-CHAIN carbon based substituents are named before the chain name. they have the prefix -yl added to the basic stem (e.g. CH3 is methyl).

Number the principal chain from one end to give the lowest numbers.

Side-chain names appear in alphabetical order butyl, ethyl, methyl, propyl

Each side-chain is given its own number.

If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa

Numbers are separated from names by a HYPHEN e.g. 2-methylheptane

Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane

Example longest chain 8 (it is an octane)3,4,6 are the numbers NOT 3,5,6order is ethyl, methyl, propyl

3-ethyl-5-methyl-4-propyloctane

Alkyl radicals methyl CH3 - CH3

ethyl CH3- CH2- C2H5

propyl CH3- CH2- CH2- C3H7

CH3

CH2 CH3CH

CH2

CH2CH3 CH

CH

CH2

CH2CH3 CH2

CH3



CH3

CH2CH3 CH3CH

CH2

CH3


Apply the rules and name these alkanes

CH3

CH3CH

CH2

CH2CH3 CH

CH3

THE ANSWERS ARE ON THE NEXT SLIDE


CH3

CH2CH3 CH3CH

CH2

CH3


CH3

CH3CH

CH2

CH2CH3 CH

CH3




CH3

CH2CH3 CH3CH

CH2

CH3


CH3

CH3CH

CH2

CH2CH3 CH

CH3

Longest chain = 5 so it is a pentane

A CH3, methyl, group is attached to the third carbon from one end...

3-methylpentane




CH3

CH2CH3 CH3CH

CH2

CH3


CH3

CH3CH

CH2

CH2CH3 CH

CH3



3-methylpentane



Longest chain = 6 so it is a hexane

A CH3, methyl, group is attached to the second carbon from one end...

2-methylhexane


CH3

CH2CH3 CH3CH

CH2

CH3


CH3

CH3CH

CH2

CH2CH3 CH

CH3



3-methylpentane




A CH3, methyl, group is attached to the second carbon from one end...

2-methylhexane


CH3, methyl, groups are attached to the third and fourth carbon atoms (whichever end you count from).

3,4-dimethylhexane

Discuss examples Page 430

Name the following hydrocarbons:(a)C(CH3)4

(b)CH3CH(C2H5)CH3

(c)CH3CH2CH(C2H5)CH2CH3

Belongs to the homologous series of saturated hydrocarbons

- Contain only single covalent bonds between atoms in molecules.

- Contain only hydrogen and carbon atoms

Alkanes hydrocarbons that contain only single bonds

Each one different from previous by

1 C and 2 H

Can be represented by a general formula. Physical property changes gradually as the

number of CH2 group increases.

Have similar chemical properties (since they have the same functional groups)

For alkanes with 3 or less C atoms, only 1 molecular structure possible

In alkanes with more than 3, chains can be straight or branched

So, alkanes with 4 or more C have structural isomers

Names Molecluar

Formula

Mr Empirical

Formula

Condensed Formula

Bpt /0 C

State Full structural formula

Methane CH4 16 CH4 CH4 -164 Gas

Ethane 30 -89 Gas

Propane C3H8 44 C3H8 CH3CH2CH3 -42 Gas

Butane 58 -0.5 Gas

Pentane C5H12 72 +36 Liquid

Hexane C6H14 CH3 (CH2) 4CH3 liquid

Name ends with –ane and has a general molecular formula CnH2n+2

Alkanes with lowest molecular mass (1-4 C atoms) are gases

Natural gas fossil fuel made primarily of alkanes containing 1-4 C atoms

C-H bonds are nonpolar Only forces of attraction between nonpolar

molecules are weak intermolecular forces

The strength of the forces is related to the no. of electrons involved in the structure and the surface area of the molecules over which the interactions can be spread.

Increasing the chain length of the molecules increase both these features and so the strength of the van der Waals’ forces increases with the increasing molecuar size.

Physical properties dependent on these interactions, such as mpt, bpt and enthalpy of vaporisation will also increase with the length of chain.

Larger alkanes are liquid Gasoline, kerosene made mostly of liquid

alkanes Stronger forces hold together enough to

form liquids Alkanes with very high molecular mass are

solid Paraffin wax contains solid alkanes

(candles)

Increase with increasing molecular mass As the strength of the van der Waals’ forces

increases, more energy (heat) required to break them

This property used in separation of petroleum (major source of alkanes)

Petroleum complex mixture of different hydrocarbons that varies greatly in composition

Petroleum is a mixture of hydrocarbon molecules from 1 to more than 50 C atoms is heated in a furnace. Oil vaporizes and passes up the fractionating column.

The different fractions come out of the column at different heights depending on their boiling points.

Substances with low boiling points are collected near the top of the column

A hydrocarbon with a long chain has __________________than one with a shorter carbon chain

higher boiling point

Fractions Boiling (0C)

Approx no. of C atoms

Petroleum gas

Below 40 1-4

Petrol (gasoline)

40-75 5-10

Naphtha 75-150 7-14

Kerosene (paraffin)

160-250 11-16

Diesel Oil 250-300 16-20

Lubricating Oil

300-350 20-35

Bitumen Above 350 More than 70

As the no. of C atoms increases,

• boiling point increases• liquids are more viscous• liquids burn less easily

To meet the demands for fractions like petrol and kerosene, a process called cracking is carried out.

This involves the use of high temperature, pressure and catalyst to split the larger molecules (of higher boiling points) into smaller ones (of lower boiling points)

ExampleC10H2 C10H22 + C10H22

Belongs to the homologous series of unsaturated hydrocarbons.

- Contains double covalent bonds between C atoms in molecules.

- Contain only H and C atoms.

Draw the dot and cross diagram of ethene

Name formula Mr Full structural formula

Ethene C2H4 28

Pro-1-pene C3H6 42

But-1-ene C4H8 56

Pent-1-ene C5H10 70

Hex-1-eneImportant plant hormone – induces flowering and ripening of fruit

Butene has 3 isomers: 1st isomer 2nd isomer 3rd

isomer

Condensedformula

Draw all the isomers of C5H10 and write their condensed formulae.

Page 440

NAMING ALKENESNAMING ALKENES

Length In alkenes the principal chain is not always the longest chain It must contain the double bond the name ends in -ENE

Position Count from one end as with alkanes. Indicated by the lower numbered carbon atom on one end of the C=C bond

5 4 3 2 1

CH3CH2CH=CHCH3 is pent-2-ene (NOT pent-3-ene)

Side-chain Similar to alkanes position is based on the number allocated to the double bond

1 2 3 4 1 2 3 4

CH2 = CH(CH3)CH2CH3 CH2 = CHCH(CH3)CH3

2-methylbut-1-ene 3-methylbut-1-ene

Name the following alkenes:(a) (b) CH3CH2CH(CH3)CH= CH2

(c) (d) CH2= C(CH3)CH2CH= CH2

Name formula Full structural formula

Methanol

Ethanol C 2H5OH

Propan-1-ol C3H7OH

Butan-1-ol C4H9OH

Pentan-1-ol

general formula CnH2n+1OH or R-OHLower members are very soluble in water because of hydrogen bonding

Alcohols are the homologous series with the general formula CnH2n+1OH.

They all contain the functional group, OH, which is called the hydroxyl group.

Alcohols can be classified as primary, secondary or tertiary, depending on the carbon skeleton to which the hydroxyl group is attached.

Draw out the structure, name and classify all the alcohols with the formula C4H9OH.

RCH2OH1 alkyl group on C next to

OH so primary

alcohol, 1°

R2CHOH2 alkyl groups on C next to

OH so secondary alcohol, 2°

R3COH3 alkyl groups on C next to

OH so tertiary alcohol, 3°

OHH

H

C

H

H

C

H

H

C

H

H

C

H

Butan-1-ol primary

OH

H

H

C

H

H

C

H

H

C

H

H

C HButan-2-ol secondary

OHH

H

C

H

H

C

H

H

C

CH3

OH

H

H

C

H

H

C

H

HC

CH3

2-methylpropan-1-ol primary

2-methylpropan-2-ol tertiary

Page 448

Draw the isomers of propanol.


Methanal HCHO

Ethanal CH3CHO

Propanal C2H5CHO

Butanal

general formula CnH2n+1CHO or R-CHO

Name and draw the full structural formula of

CH3CH2CH2CH(CH3)CHO


Propanone CH3COCH3

Butanone CH3COC2H5

general formula R-CO-R’ where R’ represents eitherThe same alkyl group as R or a differen alkyl group

Draw the full structural formula of pentan-2-one and write its condensed formula.

Aldehydes and ketones have very similar boiling points.

Aldehyde has higher b. pt. than alkane of similar RMM and lower b. pt. than alcohols of similar RMM.

Aldehydes are polar due to the very electronegative O, whereas alkanes are non-polar.

IMF between aldehyde molecules are stronger than those in alkane of similar RMM due to dipole-dipole interaction but only van der Waals forces are present between alkane molecules. Hence aldehydes have higher bpt than alkanes.

Alcohols are polar and its O is joined directly to H – able to form H bonding.

Since strength of hydrogen bond > dipole-dipole interaction, alcohol has higher bpt than aldehydes.

Lower members (methanal, ethanal, propanal, propanone, butanone) are soluble in water since they form H bonding with water.

Aldehyde cannot H bond to each other but able to form H bond with water.

Solubilty decreases with increasing length of HC chains because of the non-polar nature of the HC chain.


Methanoic acid

HCOOH

Ethanoic acid CH3COOH

Propanoic acid C2H5COOH

general formula R-COOH or R-CO2H

Name the following organic compound and write its condensed formula.

Practice Page 455

Carboxylic acids have H bonding between molecules. They have higher bpt. than aldehydes and alcohols of similar RMM.

Carboxylic acids have two O atoms per molecule, hence have stronger H bonding than alcohols which has only one O atom per molecule. Therefore, carboxylic acids have higher bpt. than alcohols.

Carboxylic acids with lower RMM are generally soluble in water and less soluble when the HC chain increases.

Named by using name of the alkane from which they are derived with the prefix chloro-, bromo- or iodo-.

For example:

CH3CH2Br is bromoethane

(CH3)2CHCH2Cl is 1-chloro-2-methylpropane

Remember the position of the halogen atom must be indicated using the appropriate number so

CH3CH2CH2Cl is 1-chloropropane andCH3CHClCH3 is 2-chloropropane

Halogenoalkanes can be classified in the same way as alcohols.


Iodomethane

1-bromo-3-fluoro-pentane

general formula R-X where X = F, Cl, Br or I

Key feature of halogenoalkanes is

C X C X where X = Cl, Br or I

What is notable about this bond compared with say, C – C and C – H?

The halogen atom is more electronegative than C so the bond is polarised:

C XC X

++ --

C ClC Cl

++ --

C IC I

++ --

ORDER OF BOND POLARITIES:

C BrC Br

++ --

>> >>

So is order of reactivity:

chloroalkane > bromoalkanes > iodoalkanes?

Is there another factor that ought to be considered before reaching a conclusion?

BOND ENERGIES

Bond energies:

Bond Bond energy in kJmol-1

C - Cl

C - Br

C - I

346

290

234

This suggests that the order of reactivity is:iodoalkane > bromoalkanes > chloroalkanes

No. of C atoms Halogenoalkanes have higher bpt. than

alkanes with the same no. of C atoms. Due to the higher RMM and hence stronger

van der Waals’ forces.

Refer to table Page 456

Compounds of same RMM Bromo- and iodo-compounds have substantially

lower bpt. than alkanes of similar RMM. Alkanes have longer chain molecules – in the

liquid state – more S. A. Of molecules in contact – stronger IMF.

Little difference between bpt of alkanes and chloroalkanes of similar RMM.

The chloroalkanes are polar but alkanes are non-polar – expect to have higher bpt but is balanced out by the long HC chain of alkanes.

Refer to table Page 456

Sparingly soluble or insoluble in water Soluble in organic solvent


Methylamine

2-aminobutane

general formula R-NH2

Strong smelling substances

Page 465


Methyl methanoate

Propyl ethanoate

general formula R-COOR’, where R’ is an alkyl group


Benene C6H6

Methyl benzene

Are the following molecules primary, secondary or tertiary?(a)3-methylpentan-3-ol(b)Pentan-2-ol(c)1-chlorobutane

Are the following molecules primary, secondary or tertiary?

(a)3-methylpentan-3-ol(b)Pentan-2-ol(c)1-chlorobutane

also referred to as noncovalent interactions or nonbonded interactions.

several types of intermolecular interactions.

What type of intermolecular force would you expect to find between alkanes, halogenoalkanes, aldehydes, ketones, alcohols and carboxylic acids?

Use this information to deduce the relative boiling points of these homologous series and their solubility in water.

Ionic compounds contain oppositely charged particles held together by extremely strong electrostatic interactions.

These ionic interactions are much stronger

than the intermolecular forces present between covalent molecules.

are weak interactions caused by momentary changes in electron density in a molecule.

the only attractive forces present in nonpolar compounds.

Even though CH4 has no net dipole, at any one instant its electron density may not be completely symmetrical, resulting in a temporary dipole. This can induce a

temporary dipole in another molecule. The weak interaction of these temporary dipoles constituents van der Waals forces.

van der Waals forces are also affected by polarizability.

Polarizability is a measure of how the electron cloud around an atom responds to changes in its electronic environment.

Larger atoms, like iodine, which have more loosely held valence electrons, are more polarizable than smaller atoms like fluorine, which

have more tightly held electrons. Thus, two F2 molecules

have little attractive force between them since the electrons are tightly held and temporary dipoles are difficult to induce.

Hydrogen bonding typically occurs when a hydrogen atom bonded to O, N, or F, is electrostatically attracted to a lone pair of electrons on an O, N, or F atom in another molecule.

In boiling, energy is needed to overcome the attractive forces in the more ordered liquid state.

The stronger the intermolecular forces, the higher the boiling point.

For compounds with approximately the same molecular weight:

Consider the examples below which illustrate the effect of

size and polarizability on boiling points.

The intermolecular forces increase with increasing polarization of bonds.

Strength of forces (and therefore impact on boiling points) is ionic > hydrogen bonding > dipole dipole > van der Waals’ forces

Boiling point increases with molecular weight, and with surface area.

A measure of how easily a substance evaporates. A high volatile substance evaporates easily and has a low boiling point.

3 factors that affect the volatility Volaility decreases with the increasing

molecular size. The longer molecule with increased molecular size has stronger van der Waals’ force between the molecules, hence increasing boiling point. Hence, the early molecules are gases and liquids while the later molecules are mostly soilds.

A branched isomer of the compound is likely to have a lower boiling point than its straight chain isomer.

The branching of a chain results in a more spherical overall shape to the molecule. This means there is less contact surface area between molecules and these branched isomers have weaker intermolecular forces and hence lower boiling points.

The nature of the functional group present will influence the volatiity, depending on the effect of intermolecular forces.

Polar groups will have stronger dipole-dipole interactions between molecules hence higher boiling points.

Groups that are capable of forming hydogen bonds will result in even stronger forces between the molecules, giving rise to even higher boiling points.

In melting, energy is needed to overcome the attractive forces in the more ordered crystalline solid.

The stronger the intermolecular forces, the higher the melting point.

Given the same functional group, the more symmetrical the compound, the higher the melting point.

The trend in melting points of pentane, butanal, and 1-butanol parallels the trend observed in their boiling points.

Solubility is the extent to which a compound, called a solute, dissolves in a liquid, called a solvent.

In dissolving a compound, the energy needed to break up the interactions between the molecules or ions of the solute comes from new interactions between the solute and the solvent.

An organic compound is water soluble only if it contains one polar functional group capable of hydrogen bonding with the solvent for every five C atoms it contains.

For example, compare the solubility of butane and acetone in H2O and CCl4.

To dissolve an ionic compound, the strong ion-ion interactions must be replaced by many weaker ion-dipole interactions.

The nonpolar part of a molecule that is not attracted to H2O is said to be hydrophobic.

The polar part of a molecule that can hydrogen bond to H2O is said to be hydrophilic.

In cholesterol, for example, the hydroxy group is hydrophilic, whereas the carbon skeleton is hydrophobic.

Soap molecules have two distinct parts—a hydrophilic portion composed of ions called the polar head, and a hydrophobic carbon chain of nonpolar C—C and C—H bonds, called the nonpolar tail.

On the other hand, alkyl halides possess an electrophilic carbon atom, so they react with electron rich nucleophiles.

Introduction Special nature of carbon Classification of Organic Chemistry Homologous Series &...

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