chapter 8 compounds of carbon

7/28/2019 Chapter 8 Compounds of Carbon

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Hydrocarbons / Organic

Chemistry


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Organic Chemistry

Organic chemistry is the study of the

structure, properties, composition,

reactions, and preparation of the chemical

compounds that contain carbon.


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Hydrocarbons

Hydrocarbons are molecules which

contain hydrogen and carbon

There are many different compounds

that can form with carbon and hydrogen

There are 3 main hydrocarbon families

1. Alkane

2. Alkene3. Alkyne


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Where do you find hydrocarbons? Carbon compounds make up 90% of all

chemical compounds and many form thebasis of living systems

The majority of hydrocarbons found

naturally occur in crude oil Crude oil forms from decomposed organic

matter which has lots of carbon and

hydrogen!. Proteins, carbohydrates and fats

all contain carbon, hydrogen and

oxygen


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What are the differences and

similarities of the compounds below


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1. Alkanes Are hydrocarbons that contain only carbon

and hydrogen They only have single bonds

CnH2n + 2

A series of compounds with similarproperties in which each member differs

from the previous one by CH2 is known as

a homologous series Structural formulas show the number and

location of bonds but not lone pairs


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Straight and branched chain A straight-chain is where the carbon atoms in an

alkane, alkene and alkyne form a chain that runsfrom one end of the molecule to the other.

A branched chain is were an alkane, alkene and

alkyne has alkyl groups bonded to its central

carbon chain. An alkyl is a group of atoms consisting of carbon

and hydrogen atoms, arranged in a chain.


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Naming carbon compounds

No. of carbon

Atoms

Prefix

1 Meth-

2 Eth-

3 Prop-

4 But-

5 Pent-

6 Hex-

7 Hept-

8 Oct-

9 Non-


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What are the differences and

similarities of the compounds below


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2. Alkenes Contains at least one carbon to carbon

double bond

The alkenes are a homologous series

CnH2n n = integer


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Naming Alkenes Carbon atoms are

labelled from left toright

Identify where the

double bond starts

And put that numberbetween the prefix

and suffix of the

alkene

But-1-ene

But-2-ene


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Naming alkenes with 2 double

bonds

If there are two

double bonds the

suffix (ending) is -

diene 3 double bonds -

triene

buta-1, 2-diene


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3. Alkynes

Are hydrocarbons that contain only carbon

and hydrogen

They have at least one triple bond

The alkynes are a homologous series


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Naming carbon compounds

Suffix

If all of the carbon to carbon

bonds are single

-ane

If there is at least one carbon-

carbon bond is a double bond

-ene

If there is at least one carbon-

carbon bond is a triple bond

-yne


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Structural isomers Structural isomers are molecules with the

same molecular formula but differentarrangement of their atoms (different structural

formulas)


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Structural Isomers


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Structural isomers


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Semi-structural formulas

Semi- structural formula is a structural

formula without giving the arrangement

atoms in space


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Make and then draw as many

isomers of hexane as possible


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N i i


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Naming isomers1. Name and number longest carbon chain (circle it)

2. Identify branches (there are no branches at ends!)

3. Name each branch (alkyl group) put them in

alphabetical order

methyl CH3 ethyl C2H5 propyl C3H7 butyl C4H9

pentyl C5H11

4. If there is more than 1 alkyl group use:

di = 2, tri = 3, tetra = 4 as a prefix e.g. diethyl, trimethyl

5. Write the number of the carbon atom each alkyl groupis attached to. Put commas between numbers if there

is more than one alkyl group (2,3-dimethyl)

6. Put hyphens between numbers and words (2,2

dimeth lbutane


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Name the following

n

2-methyl propane

propane


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Name the following carbon

compounds

5-ethyl-5,6,6-trimethyl

decane

4,5-diethyl-5,6-dimethyl-

4-propyloctane


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Are these

namedcorrectly?

Rewrite the

names that

areincorrect


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Name all the isomers of hexane you drew


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Saturated compounds

A saturated compound has no double or triplebonds.

In saturated linear hydrocarbons, every carbon

atom is attached to two hydrogen atoms, except

those at the ends of the chain, which have threehydrogen atoms.

In the case of saturated methane, four hydrogen

atoms are attached to the single, central carbonatom.

Of simple hydrocarbons, alkanes are saturated,

and alkenes are unsaturated.


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Unsaturated carbon compounds

Alkenes and alkynes are unsaturated

carbon compounds because they contain

less hydrogen than the maximum amount

possible


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Which compound/s are saturated?

v


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Physical Properties of Alkanes

and Alkenes As the number of carbon atoms increases

in a homologous series there is a change

in the physical properties

At room temperature, the lighter alkanesand alkenes are gases; the midweight

alkanes are liquids; and the heavier

alkanes are solids, or tars. Why?

London forces increase as molecules get

heavier


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Boiling Point

The boiling points of thealkanes and alkenes

gradually increase with

the molecular weight of

the compounds. Alkanes and alkenes

have similar boiling

points

Alkenes have a slightly

lower

Hydrocarbons Boiling point(C)

Methane -161.5

Ethane -88.6

Propane -42.1

Butane -0.5

Pentane 36.1


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Volatility Volatile liquids are those

that evaporate (go fromliquid to solid) easily.

Smaller molecules are

more volatile

Why?

Because there are weak

London forces so it is

easier for them to go froma liquid to a gas

Viscosity


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Viscosity Viscosity is the measure of the thickness of a

fluid

Honey is more viscose (it is harder to pour)than water

The larger the molecule the more viscous it is

The larger the molecule the stronger theLondon forces which means they are morelikely to stick together because they are longthey get tangled up like spaghetti


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Hydrocarbon Solubility

The rule to use when determining

hydrocarbon solubility is: Like dissolves

like.

This means that polar compounds (water,

and alcohols) dissolve other polar

compounds.

Nonpolar compounds dissolve other

nonpolar compounds but tend not to

dissolve polar compounds.


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Chemical Properties of Alkanes Alkanes burn in oxygen this is called a

combustion reaction The reactants are hydrocarbon and oxygen

The products are water and carbon dioxide


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Combustion reaction Combustion reactions are whats causing

global warming!

Petrol, made up of hydrocarbons

combusts in cars engines


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Chemical Properties of Alkenes

Alkenes have different chemical properties

to alkanes due to the double bonds in

alkenes

Alkenes react much more readily than

alkanes

R ti ith b i l ti


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Reaction with bromine solution Ethene reacts with bromine and bromine is

added to the ethene molecule. Ethene loses itsdouble bond

This is called an addition reaction because

bromine is added to ethene


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Reaction with bromine solution

This is used to test for unsaturation

If the solution is unsaturated the red brown

colour of bromine disappears

The red brown colour disappears becasue

the bromine becomes part of the ethene

molecule

Permanganate solution is also used to test

for unsaturation

T t f t ti


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Test for unsaturation Bromine does not react with an alkane

because the alkane contains only singleC-C bonds which cannot add the bromine.

Alkanes merely dilute the red-brown

bromine color to an orange or yellow color Due to their C=C double bonds which can

be broken, alkenes react readily with

bromine to produce saturateddibromoalkanes.


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Reaction of alkane with halogens

The reaction of alkanes follows thegeneral rule

Br2 + alkane alkaneBr + HBr


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Ethene and Hydrogen reaction

Ethene reacts with hydrogen gas to form

ethane

This is an example of an addition reaction


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Reaction with steam

Ethene reacted with steam (water) forms

ethanol

F ti l id f


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Functional groups aside from

alkyl groups

OH, hydroxy alkanolFunctional group Name of functional

group

Homologous series


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http://www.sciencegeek.net/APchemistry/

APtaters/alkanes.htm

chapter 8 compounds of carbon

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