Chemistry - Chapter 11/12

Basic concepts of organic chemistry + alkanes

What is a hydrocarbon?

A compound containing only carbon and hudrogen

What are the 2 types of hydrocarbons?

Saturated - only single bonds

Unsaturated - contains carbon-carbon multiple bonds

What is a homologous series?

A family of compounds with the same functional group but each successive member differing by CH2

What is the functional group?

A group of atoms responsible for the characteristic reaction of a compound

What are the 3 ways hydrocarbons can be classified?

Aliphatic - compounds containing carbon atoms joined in straight chains

Alicyclic - a compound containing carbon atoms joined in rings (not a benzene ring) with/without side chains

Aromatic - a compound containing a benzene ring

What are the 3 homologous series of aliphatic hydrocarbonds?

Alkanes - containing single C-C bonds

Alkenes - containing double C=C bonds

Alkynes - containing at least one triple C-C bond

What is the stem, prefix and suffix?

Stem - part of the name indicated number of carbon atoms in the longest continuous chain in the molecule

Prefix - added before the stem and indicates the presence of side chains and/or functional groups

Suffix - added after the stem to indicate the functional group

What are the 4 steps in naming aliphatic alkanes?

1 - All alkanes have suffix -ane

2 - Identify longest continuous carbon chain (“parent chain“) and name it

3 - Identify any side chain (“alkyl groups“) name of this group added as a prefix to name of parent chain

4 - Add number before any alkyl groups to show position of alkyl groups on the parent chain

What happens to an alkyl group’s formulae?

It has a hydrogen removed from a parent alkane e.g. methane = CH4, (- 1X hydrogen) methyl = CH3

What is the alkane and alkyl for 1 carbon atom?

Methane - CH4

Methyl - CH3

What is the alkane and alkyl for 2 carbon atom?

Ethane - C2H6

Ethyl - C2H5

What is the alkane and alkyl for 3 carbon atom?

Propane - C3H8

Propyl - C3H7

What is the alkane and alkyl for 4 carbon atom?

Butane - C4H10

Butyl - C4H9

What is the alkane and alkyl for 5 carbon atom?

Pentane - C5H12

Pentyl - C5H11

What is the alkane and alkyl for 6 carbon atom?

Hexane - C6H14

Hexyl - C6H13

What is the alkane and alkyl for 7 carbon atom?

Heptane - C7H16

Heptyl - C7H15

What is the alkane and alkyl for 8 carbon atom?

Octane - C8H18

Octyl - C8H17

What is the alkane and alkyl for 9 carbon atom?

Nonane - C9H20

Nonyl - C9H19

What is the alkane and alkyl for 10 carbon atom?

Decane - C10H22

Decyl - C10H21

What happens when there are two or more possible chains of the same length within a molecule?

The chain with the most branches is considered the longest chain

What is the process for naming alicyclic alkanes?

Same as naming aliphatic alkanes, but the prefix cyclo- is added to front of the stem to show that the carbon atoms are arranged in a ring structure

How are alkenes names?

Same process as alkanes, but suffix is -ene. The position of the C=C must be names in alkenes that have four or more carbon atoms in the longest chain e.g. pent-2-ene

In alkenes, if the C=C is between C2 and C3, which position is named?

The smallest number needed to indicate position of double bond, so we use 2- only e.g. pent-2-ene

What are the 4 steps to naming an alkene?

1 - Identify which suffix to use

2 - Identify longest continuous chain of carbon atoms

3 - Identify where the double bond is

4 - Combine suffix, stem and position of C=C to name the compound

What are the 3 steps for naming compounds containing functional groups?

1 - Identify the longest unbranched chain of carbon atoms, the stem is is the name of the corresponding alkane

2 - Identify any functional groups/alkyl side chains and select the appropriate prefixes or suffixes for them

3 - Number any alkyl/functional groups to indicate their position on the longest unbranched chain

What are the 11 common functional groups?

Alkene, alkane, alcohol, haloalkane, aldehyde, ketone, carboxylic acid, ester, acyl chloride, amine, nitrile

What is the functional group name/structure/suffix of alkanes?

Name - alkyl

Structure - R-H

Suffix - -ane

What is the functional group name/structure/suffix of alkenes?

Name - alkenyl

Structure - C=C

Suffix - -ene

What is the functional group name/structure/prefix of haloalkanes?

Name - halo (-Cl/-Br/-I)

Structure - R-X (R=C/H and X= halogen)

Prefix - e.g. -chloro/-bromo/-iodo

What is the functional group name/structure/suffix/prefix of alcohols?

Name - hydroxol (-OH)

Structure - R-OH

Suffix - -ol

Prefix - hydroxy-

What is the functional group name/structure/suffix of an aldehyde?

Name - carbonyl (-CHO)

Structure - R-C (C=O and C-H)

Suffix - -al

What is the functional group name/structure/suffix of ketones?

Name - carbonyl (-C(CO)C-)

Structure - R-C (C=O and C-R) also R can only be H atoms/alkyl groups

Suffix - -one

What is the functional group name/structure/suffix of carboxylic acids?

Name - carboxylate (-COOH)

Structure - R-C (C=O and C-OH)

Suffix - -oic acid

What is the functional group name/structure/prefix/suffix of amines?

Name - Amine (-NH2)

Structure - R-N (N single bonded to R 2X) R can be H atoms/alkyl groups

Prefix - amino-

Suffix - -amine

What is the rule with amines?

Amine is the main part, anything attached to NH2 group is side chain

What is the functional group/structure/suffix of ester?

Group - -COOC-

Structure - -C=O (C single bonded to O-C)

Suffix - -oate

What is the functional group/structure/suffix of acyl chloride?

Group - -COCl

Structure - -C=O (C-Cl as well)

Suffix - -oyl chloride

What is the functional group/suffix of nitrile?

Group - -CN

Suffix - -nitrile

What are the 4 steps in naming alcohols?

1 - Identify functional group and suffix

2 - Identify longest chain of carbon atoms

3 - Identify which carbon atom the functional group is on

4 - Combine suffix and stem to name the compound e.g. butan-2-ol

What is the rule with suffix consonants in naming?

Remove final letter -e from alkane stem when suffix starts with a vowel. Keep final letter -e of the alkane stem when the suffix starts with a consonant

What are the 3 steps in naming adelhydes?

1 - Identify functional group and suffix

2 - Identify longest chain of carbon atoms

3 - Combine suffix and stem to name the compound. Adelhydes do not need numbers to show position of the carbonyl group (it is always on position 1)

What are the 3 steps in naming multiple functional groups?

1 - Identify longest chain of carbon atoms

2 - Identify the functional groups present, which carbon atom they are on, and the prefixes

3 - Combine stem and prefixes to name compound, remember side chains are named in alphabetical order

What are the 6 types of formulae?

Molecular, empirical, general, displayed, structural, skeletal

What is the molecular formula?

Shows the number and type of atoms of each element present in a molecule, does not show how atoms are joined, different molecules can have same molecular formula

What is the empirical formula?

Simplest whole-number ratio of the atoms of each element present in a compound

What is the general formula?

Simplest algebraic formula for any member of a homologous series, you can use the general formula to generate the molecular formula for any member of that homologous series

What is the general formula of alkanes?

CnH2n+2

What is the general formula of alkenes?

CnH2n

What is the general formula of alcohols?

CnH2n+1OH

What is the general formula of carboxylic acids?

CnH2nO2

What is the general formula of ketones?

CnH2nO

How are alcohols exceptional from these rules?

The general formulae and molecular formula for alcohols are different. General formula = CnH2n+1OH and the molecular formula = CnH2n+2O

What is the displayed formula?

Shows relative positioning of all of the atoms in a molecule and the bonds between them

What is the structural formula?

Uses the smallest amount of detail necessary to show arrangement of the atoms in a molecule, it shows clearly which groups are bonded together e.g. structural formula of butane is CH3(CH2)2CH3

What is the skeletal formula?

It is a simplified organic formula, you remove:

* All of the carbon/hydrogen labels from carbon chain
* Any bonds to H atoms

This leaves just a carbon skeleton and any functional groups

In skeletal formula:

* A line represents a single bond
* An intersection of two lines represents a carbon atom
* The end of a line represents a -CH3 group

What are some of the most common uses of skeletal formula?

Representing alicyclic and aromatic compounds

What happens when functional groups involved in skeletal formula?

They are added onto skeletal formula diagram a line(s) showing bonding from atom to functional group(s)

What are isomers?

Different compounds with the same molecular formula and different structural formula

What are the 2 types of isomerism?

Structural isomers and sterioisomers

What is stereoisomerism?

Have same structural formula but 3D arrangement of atoms is different

What are the 2 types of steroisomerism?

Cis-trans isomerism and optical isomerism

What is structural isomers?

Have different structural formula same molecular formula, three types of structural isomers: chain, positional and functional group isomerism

What is chain isomerism?

The carbon chain is arranged differently

What is positional isomerism?

The functional group is attached to a different carbon atom, only exists in alkenes with four or more carbon atoms

What is functional group isomerism?

Contain different functional groups and so are members of different homologous series e.g. both alcohols and ethers have same general formula so may be functional group isomers

What are the 8 steps in drawing isomers?

1 - Draw longest carbon chain first

2 - If there is a functional group put it on C1, then move it down the chain drawing each isomer until no more can be made

3 - Remove a carbon from the chain and add it as a methyl group to C2, repeat step 2 if there is a functional group

4 - Move methyl group down chain repeating step 2 until no more isomers can be drawn

5 - If carbon chain long enough, remove another C atom and put 2 methyl groups of C2, repeat step 2

6 - Repeat step 4 if more than 3 C atoms in the chain until no more side chain can be produced

7 - Check to see if any ethyl groups can be made

8 - If an alkene is present remember to do cyclic alkanes and side chains

What 2 ways can covalent bonds be broken?

Homolytic and heterolytic fission

What is fission?

When a covalent bond is broken

What is homolytic fission?

When the covalent bond breaks and each atom gets back their own electron, this results in a free radical (there is an unpaired electron)

What 2 things are created in homolytic fission?

1 - Each atom now has a single unpaired electron

2 - An atom/groups of atoms with an unpaired electron is called a radical

What is heterolytic fission?

When the covalent bond breaks and one atom gets both electrons, this results in ions being formed

What 2 things happen in heterolytic fission?

1 - The atom that takes both electrons becomes a negative ion

2 - The atom that does not take the electrons becomes a positive ion

What is the reaction mechanism?

An equation that tells you about how the reaction takes place

What are curly arrows used to show in a reaction mechanism?

Show the movement of electron pairs when bonds are being broken/made

What does a “half a headed arrow“ show?

Shows movement on a single electron

What does a “full arrow“ show?

Shows movement of a pair of electrons

How do you draw the arrows used in reaction mechanism equations?

The arrow must start at the centre of the bond and point to the atom which receives the electrons

What are the 3 general types of reactions?

Additions, substitution, elimination reactions

What are addition reactions?

Two reactants join together to form one product

What are substitution reactions?

An atoms/group of atoms is replaced by a different atom/group of atoms

What are elimination reactions?

Where one reactant loses a small molecule (usually H2O)

What is the nuance of addition/substitution reactions?

They usually have a word before them to describe the type of reaction in more detail (linked to its mechanism and the species attacking the molecule)

What are addition reactions (what can they be)?

They can be either electrophilic addition or nucleophilic addition reactions

What is electrophilic addition?

Involves an electrophile (an electron pair acceptor) and occurs in alkenes

What is nucleophilic addition?

Involves a nucleophile (an electron pair donor) and occurs in carbonyl compounds (adelhydes and ketones)

What are substitution reactions (what can they be)?

They are usually nucleophilic substitution and involve a nucleophile

What are alkanes the main component of?

Crude oil and natural gas

What property of them has allowed crude oil deposits to remain in Earth for many million years?

They are very stable compounds and have a lack of reactivity

What are alkanes mainly used for?

Used for fuel, exploiting their reaction with oxygen to generate heat

What is the general formula of alkanes?

CnH2n+2

What are alkanes?

Saturated hydrocarbons which only contain single covalent bonds

What is bonding in an alkane?

Type of covalent bond called sigma bonds (result from overlap of one end of p orbital with either an s orbital/another end of p orbital, can also be 2X s orbital overlapping)

What is the shape of alkanes?

Each carbon atom surrounded by 4 electron pairs in four sigma-bonds. Repulsion by these electron pairs result in a 3D tetrahedral arrangement around each carbon atom, each bond angle is 109.5 degrees

What do the sigma bonds act as within shapes of alkanes?

Act as axes around which the atoms can rotate freely, so these shapes are not rigid e.g. butane can also rotate into a U shape

What does crude oil contain?

Many different alkanes

What is crude oil separated into?

Into fractions

What is process of fractional distillation?

Oil refineries separate crude oil into fractions by fractional distillation in a distillation tower, each fraction contains range of alkanes

Why is fractional distillation possible?

Because the boiling points of alkanes are different, increasing as chain length increases

Why do boiling point increase with chain length?

Boiling point of straight chain alkanes increases with chain length due to increasing London forces between molecules. As chain length increases so does its surface area, and so London forces are stronger

What is boiling point like in branched-chain alkanes?

Lower boiling points because chains cannot pack as closely together, fewer points of contact between molecules so London forces are weaker