Organic (Y1) - Introduction to organic chemistry

Question 1

What’s a hydrocarbon?

Answer 1

A compound consisting of hydrogen and carbon ONLY.

Question 2

Define saturated

Answer 2

contain single carbon-carbon bonds only

Question 3

Define Unsaturated

Answer 3

Contains a Carbon=Carbon double bond

Question 4

Define Molecular formula

Answer 4

The formula which shows the actual number of each type of atom

Question 5

Define Empirical Formula

Answer 5

Shows the whole number ratio of atoms of each element.

Question 6

Define Structural Formula

Answer 6

shows the minimal detail that shows the arrangement of atoms in a molecule, eg for butane: CH3CH2CH2CH3 or CH3(CH2)2CH3

Question 7

Define Displayed

Answer 7

Show all the covalent bonds and atoms present in a molecule

Question 8

Think of examples of a displayed formula

Answer 8

When drawing organic compounds add the hydrogen atoms so that H each carbon has 4 bonds.

Question 9

What’s the skeletal formula?

Answer 9

shows the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional Groups.

Question 10

What’s the functional group?

Answer 10

is an atom or group of atoms which when present in different molecules causes them to have similar chemical properties.

Question 11

What are Homolgous series and can you think of any examples.

Answer 11

Homologous series are families of organic compounds with the same functional group and Same general formula.

• They show a gradual change in physical properties e.g. B.P.
• Same chemical properties
• Each member differs by CH2 from the last.

Question 12

The general rules for naming carbon chains

Answer 12

• Count the longest carbon chain and name appropriately.
• Find any branched chains and count how many carbons they contain.
• Add the appropriate prefix for each branch chain.

Question 13

What’s homolytic fission?

Answer 13

When EACH atom gets ONE electron from the covalent bond - A one headed arrow shows movement of one electron. The bond has broken in the process called homolytic fission.

Question 14

What is formed after homolytic fission?

Answer 14

2 free radicals are formed.

Question 15

What’s the definition of a free radical?

Answer 15

A free radical is a reactive species which possess an unpaired electron. Free radicals do not have a charge but are represented with a bold dot.

Question 16

What’s heterolytic fission?

Answer 16

When one atom gets both electrons - two headed arrows used to represent this.

Question 17

Define structural isomers

Answer 17

Same molecular formula different structures.

Question 18

Define Chain isomers

Answer 18

Compounds with the same molecular formula but different structures of the carbon skeleton.

Question 19

Define Position isomers

Answer 19

Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton.

Question 20

Define functional group isomers

Answer 20

Compounds with the same molecular formula but with atoms arranged to give different functional groups.

Question 21

Define stereoisomers / describe them

Answer 21

Stereoisomers have the same structural formula but different spatial arrangement of atoms.

Question 22

Why do E-Z isomers exist?

Answer 22

E-Z isomers exist due to restricted rotation about the C=C double bond. Alkenes can exhibit E-Z stereoisomerism.

Question 23

When do E-Z stereoisomers arise?

Answer 23

a) There’s a restricted rotation around the C=C double bond.

b) There are two different groups/atoms attached to both ends of the double bond.

Question 24

What’s the priority group?

Answer 24

Priority group: The atom with the bigger atomic number is classed as the priority atom.

Question 25

Steps to determining the name of E-Z Stereoisomers.

Answer 25

1) Determine the priority groups on both sides of the C=C double bond.
2) If priority atoms on the same side of the double bond it is labelled X from the german zusammen (The Zame Zide).
3) If the priority atom is on the opposite side of the double bond it is labelled E from the german entgegan (The Epposite side).

Question 26

What are the Cahn-Ingold-prelog (CIP) priority rules?

Answer 26

1. Compare the atomic number of the atoms directly attached to each side of the double bond; the atom of higher atomic number is given priority.
2. If the atoms are on the same side, consider the atoms at distance 2 from the double bond. Make a list of each atom bonded to the one directly attached to the double bond. Arrange list in order of decreasing atomic number. Compare the lists atom by atom; at earliest difference, the group containing the atom of higher atomic number is given priority.

Question 27

Effect of EZ stereoisomers on physical properties. What do you think they can do? Think of the polarity and electronegativity of bonds.

Answer 27

Some molecules may be polar and some may be non-polar. The polar molecules tend to have a higher boiling point and melting point because the bonds are stronger and therefore harder to break.