Organic key knowledge

Question 1

Saturated definition

Answer 1

Single bonds only

Question 2

Unsaturated definition

Answer 2

Carbon carbon multiple bonds (2 or more)

Question 3

Homologous series definition

Answer 3

A family of compounds w/ similar chemical properties whose successive members differ by -CH2

Question 4

Alkanes definition

Answer 4

Single carbon carbon bonds, saturated

Question 5

What is a functional group?

Answer 5

Part of an organic molecule that is largely responsible for it’s molecules properties

Question 6

Aliphatic meaning

Answer 6

Carbon atoms joined in straight, branched chains or non-aromatic rings

Question 7

Alicyclic meaning

Answer 7

Carbon atoms joined together in a ring structure

Question 8

Aromatic meaning

Answer 8

Some/all carbon atoms found in a benzene ring

Question 9

Alkenes

Answer 9

At least one C=C bond

Question 10

Prefix names

Answer 10

MEPBPH
Meth, Eth, Pro, But, Pent, Hex

Question 11

What are structural isomers?

Answer 11

Compounds with the same molecular formula but different structural formulae

Question 12

What is homolytic fission?

Answer 12

Covalent bond breaking
Each bonded atom takes one electron from the shared pair
Each atom is a radical (single unpaired e-)

Question 13

What is heterolytic fission?

Answer 13

When covalent bond breaks, one atom takes both of the bonded electrons
Forms a negative and a positive ion

Question 14

Types of reaction

Answer 14

Addition= 2 reactants to 1 product
Substitution= An atom/group is replaced by a different
Elimination= The removal of a small molecule from a larger one, 1 reactant forms 2 products

Question 15

The bonding in alkanes

Answer 15

Each carbon atom is joined to 4 other carbon atoms by single covalent bonds (sigma bonds)
Sigma bonds= Overlap of 2 orbitals (one from each atom), each overlapping orbital has 1 e-, sigma bond has 2 e- between bonding atoms, positioned on a line directly between bonding atoms

Question 16

Shape of alkanes

Answer 16

Each carbon atom is surrounded by 4 e- each in 4 sigma bonds
3D tetrahedral arrangement
109.5 degrees

Question 17

Boiling points in alkanes

Answer 17

Boiling point increases as chain length increases
London forces act between molecules in close surface contact
Increased chain length=molecules have larger SA=more surface contact available=greater London forces=more energy needed

Question 18

What is the effect of branching in alkanes on boiling point?

Answer 18

Branched isomers have lower boiling points
Fewer surface points of contact between branched molecules
Fewer London forces
Molecules cannot get as close together due to branches

Question 19

Reasons why alkanes are not very reactive

Answer 19

C-C and C-H sigma bonds are strong and are non polar

Question 20

Combustion of alkanes

Answer 20

Combust completely with a plentiful supply of oxygen
In fewer amounts of oxygen, combust incompletely producing CO or C

Question 21

Alkane reactions w/ halogens

Answer 21

React in presences of sunlight (UV)
Substitution reaction
Forms Haloalkanes

Question 22

Problems w/ radical substitution of alkanes

Answer 22

Further substitution can occur
forming molecules w/ more H atoms

Hydrogen can substitute at different parts of the chain

Question 23

Alkenes structure and bonding

Answer 23

Unsaturated hydrocarbons (double bonds)
Each carbon atom of the double bond, 3/4 e- are used in 3 sigma bonds
Other e- is in p-orbital in a pi bond
Pi bond= sideways overlap of 2 p-orbitals, 1 from each bonded atom and 1 e- from each atom, e- density is concentrated above and below the line joining the nuclei of the bonding atoms
Pi bond locks the atoms in place and prevents rotation

Question 24

Shape of the double bond in alkenes

Answer 24

Trigonal planar
3 regions of e- density
120 degrees

Question 25

What are stereoisomers?

Answer 25

Sam structural formula but a different arrangement of atoms in space E/Z= C=C only Optical= wider range of compounds

Question 26

E/Z isomerism

Answer 26

Must have C=C bond, different groups attached to each Carbon atom of the double bond E isomer= molecules diagonal Z isomer= molecules opposite

Question 27

Cis-trans isomers

Answer 27

One of the attached groups on each carbon atom has to be the same Cis= Opposite Trans= diagonal When hydrogen on each C: Cis=Z Trans=E

Question 28

When can the cis-trans system be used?

Answer 28

When each C atom in double bond is attached to a single H atom Otherwise use E/Z

Question 29

Cahn ingold prelog rules of naming

Answer 29

Higher atomic number= higher priority If groups of higher priority are on the same side of the C=C, the compound is Z Diagonally across C=C= E isomer

Question 30

Point of difference in E/Z isomerism

Answer 30

Use if the 2 atoms attached to a Carbon atom in a double bond are the same The group with the higher atomic number at the point of difference will have priority Continue down branches until different atom then one w/ higher atomic number= higher priority

Question 31

General reactivity of alkenes

Answer 31

More reactive that alkanes because of pi bond Because on outside of double bond the e- are more exposed and can undergo addition reactions more Pi bond is weaker than sigma

Question 32

Test for unsaturation

Answer 32

Add Bromine water (orange) dropwise Orange colour disappears across the double bond/decolourise Clear=has C=-C

Question 33

Explanation of electrophilic addition

Answer 33

High electron density region due to pi bond attracts electrophiles

Question 34

What are electrophiles?

Answer 34

Atom/group that is attracted to an e- rich centre and accepts an e- pair

Question 35

Markownikoff's rule

Answer 35

Primary= positive charge at end of chain, minor product, least stable(charge spread out less) Secondary=positive charge on a C atom w/ 2 C attached, major product Major product= most stable carbocation

Question 36

Properties of alcohols

Answer 36

Higher bp= H bonds stronger, more energy, polar molecules Quite soluble= polar bonds, as C chain increases get less soluble as H bond loses influences

Question 37

How to classify alcohols

Answer 37

Primary= OH is attached to C that is attached to 2 H and 1 alkyl Secondary= OH is attached to C attached to 1 H and 2 alkyl Tertiary= OH is attached to C attached to no H and 3 alkyl

Question 38

Colour change of dichromate ions

Answer 38

Orange to green

Question 39

Naming of haloalkanes

Answer 39

Like alcohols,

Question 40

Reactivity of haloalkanes

Answer 40

C-halogen bond is polar Attract nucleophiles

Question 41

What is a nucleophile?

Answer 41

An atom/group that donates a pair of e- to an e- deficinet bond

Question 42

What determines the rate of haloalkane hydrolysis?

Answer 42

The strength of the C-halogen bond C-F is strongest

Question 43

How to measure rate of haloalkane hydrolysis

Answer 43

Use Aq silver nitrate Silver halide precipitate is produced In ethanol solvent As bond strength decrease, rate of hydrolysis increases

Question 44

Evidence to disprove kekules

Answer 44

Lack of reactivty/ does not decolourose br length of bond is inbetween double and single Has a greater hydrogentation enthalpy than should be expected vs kekule

Question 45

Delocalised benzene model

Answer 45

Planar, cyclic, hexagonal 6 C and 6 H 3/4 e- in bondung 1 e- in p orbital at right amgles to plane p orbital overlap sideways= electron density ring Pi bond system 6 in pi system are delocalised