Molecular orbitals and stereochemistry - organic

Question 1

How are molecular orbitals formed

Answer 1

By atomic orbitals overlapping

Question 2

What happens when two atomic orbitals combine

Answer 2

An anti bonding and bonding molecular orbital form.

Question 3

How many electrons are in a molecular orbital

Answer 3

2

Question 4

What happens when there is an end on overlap of atomic orbitals

Answer 4

A sigma bond is formed.

Question 5

What happens when there is a side on overlap of atomic orbitals

Answer 5

A pi bond is formed

Question 6

What happens when non polar covalent atomic orbitals overlap

Answer 6

The molecular orbital will be symmetrical around the mid point of the orbital.

Question 7

What happens when polar covalent atomic orbitals overlap

Answer 7

The molecular orbital will be asymmetrical around the mid point of the orbital.

Question 8

Rule of hybridisation

Answer 8

When different atomic orbitals a set of degenerate hybrid orbitals are formed.

Question 9

Types of carbon hybridisation

Answer 9

sp3, sp2, sp

Question 10

Sp3 hybridisation
Orbital structure

Answer 10

Where carbon goes from 1s2, 2s2, 2p2
To 1s2, sp3

Question 11

sp3 molecular structure

Answer 11

Tetrahedral structure

Question 12

Type of bond in sp3 hybridisation

Answer 12

Carbon single bonds

Question 13

Sp2 hybridisation orbital structure

Answer 13

1s2, 2s2, 2p2
To 1s2, sp2 2p1

Question 14

sp2 molecular structure

Answer 14

Trigonal planar

Question 15

Type of bond in sp2

Answer 15

Carbon double bond

Question 16

Types of orbital bond in sp3

Answer 16

7 sigma bonds

Question 17

Types of orbital bond in sp2

Answer 17

5 sigma bonds and 1 pi bond

Question 18

sp orbital structure

Answer 18

1s2, 2s2, 2p2
To 1s2 sp 2p2

Question 19

Type of bond in sp hybridisation

Answer 19

Carbon triple bond

Question 20

Types of orbital bonds in sp hybridisation

Answer 20

3 sigma + 2 pi

Question 21

sp molecular structure

Answer 21

Linear

Question 22

Alkynes homologous series

Answer 22

A group of hydrocarbons with a carbon to carbon triple bond

Question 23

Alkynes general formula

Answer 23

CnH2n-2

Question 24

What is a skeletal structure

Answer 24

Where in organic chemistry we draw compounds without carbons and assume there is the maximum number of hydrogens bonded on.

Question 25

What does a benzene ring look like

Answer 25

It’s a hexagon with three lines inside for double bonds. Or a hexagon with a circle inside it.

Question 26

What does LUMO stand for

Answer 26

Lowest unoccupied molecular orbital

Question 26

What type of molecular orbital is a LUMO

Answer 26

Anti bonding

Question 27

What does HOMO stand for

Answer 27

Highest occupied molecular orbital

Question 28

What type of molecular orbital is HOMO

Answer 28

Bonding molecular orbital

Question 29

What type of light is absorbed by molecular orbitals without conjugated systems

Answer 29

UV light because the energy gap between the orbitals is so high

Question 30

What is a conjugated system

Answer 30

Where an organic substance has a chain of repeating carbon single and double bonds, creating delocalised electrons across many different atoms bonding molecular orbital.

Question 31

Conjugated system structure

Answer 31

Alternating carbon single and double bonds.

Question 32

Rule of energy gap and conjugated system

Answer 32

The larger the number of atoms in the conjugated system the lower the energy gap between the HOMO and LUMO

Question 33

Why are some organic substances coloured

Answer 33

Because they have long conjugated system which means that there is a lower energy gap between the HOMO and LUMO which means some wavelengths of light will be absorbed to promote electrons to higher energy levels, the complimentary colour will then be shown by the substance as this is the wavelengths of light reflected.

Question 34

What is a chromophore

Answer 34

A group of atoms within a molecule responsible for absorbing visible light

Question 35

Rule of chromophore and colour of compound

Answer 35

The compound will absorb the wavelengths of light which promote electrons to higher energy levels and all over wavelengths of light will be reflected, which shows the colour of the compound.

Question 36

How do indicators work

Answer 36

The indicator goes from deionised to ionised which forms a large conjugated system and makes the indicator change colour.

Question 37

Example of indicator

Answer 37

Phenolphthalein

Question 38

Stereoisomers definition

Answer 38

Where a molecule has the same molecular and structural formula but different 3D arrangement in space.

Question 39

Geometric isomers examples

Answer 39

Carbon to carbon double bonds and cyclo ring structure molecules.

Question 40

Cis

Answer 40

When the two groups are on the same side.

Question 41

Trans

Answer 41

Where the two groups are on different sides.

Question 42

Rules of geometric isomerism

Answer 42

For geometric isomerism to occur there must be two different groups attached to the carbon atoms that make up the bond with restricted rotation.

Question 43

How do geometric isomers differ

Answer 43

Influences chemical properties Influences physical differences

Question 44

Chemical properties example

Answer 44

Undergoes condensation or not

Question 45

Physical differences

Answer 45

Difference in mp/ bp

Question 46

Geometric isomers definition

Answer 46

Stereoisomers which have two different groups attached to carbon atoms that make up a bond with restricted rotation.

Question 47

Optical isomers

Answer 47

Stereoisomers which are non super imposable mirror images of each other.

Question 48

Enantiomers

Answer 48

Optical isomers (interchangeable)

Question 49

Chiral centre

Answer 49

A carbon atom in an optical isomers where there are four different groups attached.

Question 50

Enantiomers properties

Answer 50

In chiral environments they have different physical and chemical properties In normal environments they have the same properties.

Question 51

How to distinguish Enantiomers

Answer 51

They rotate polarised light in an equal and opposite way.

Question 52

What is optically active

Answer 52

When Enantiomers rotate polarised light in an equal and opposite way.

Question 53

Racemic mixture

Answer 53

Enantiomers of equal proportions which aren’t optically active.