AS - Intro To Organic

Question 1

What does a general formula show?

Answer 1

An algebraic formula that can describe any member of a family of compounds.

E.g - CnH2n+1 for all alcohols.

Question 2

What does an empirical formula show?

Answer 2

The simplest ratio of atoms of each element in a compound.

E.g - ethane, C2H6 has the empirical formula CH3.

Question 3

What does molecular formulae show?

Answer 3

The a steal number of atoms of each element in a molecule.

Question 4

What does structural formulae show?

Answer 4

Shows the atoms carbon by carbon, with the attached hydrogens and functional groups.

E.g - CH3CH2CH2CH2OH

Question 5

What does skeletal formulae show?

Answer 5

Shows the bonds of the carbon skeleton only, with any functional groups. The hydrogen and carbon atoms are not show.

E.g - /\/\OH

Question 6

What does displayed formulae show?

Answer 6

Shows how all the atoms are arranged, and all the bonds between them.

Question 7

How are branches in the carbon chains shown in structural formulae?

Answer 7

In brackets.

Question 8

What is a homologous series?

Answer 8

A group of compounds containing the same functional group.

Question 9

What is a functional group?

Answer 9

A reactive part of a molecule which gives most of its chemical properties.

Question 10

What is the first step to naming an organic compound?

What are the names of the first 6 stems?

Answer 10

Count the carbons in the longest continuous chain that contains the functional group.

1. Meth- 2. Eth- 3. Prop- 4. But- 5. Pent- 6. Hex-

Question 11

What gives you the suffix when naming an organic compound?

Answer 11

The main functional group.

Question 12

How should you number the carbons when naming an organic compound?

Answer 12

Number the carbons in the longest carbon chain so that the carbon with the main functional group attached has the lowest possible number.

If there’s more than one longest chain, pick the one with the most side chains.

Question 13

How are side chains and the less important functional groups added into the name?

Answer 13

Added as prefixes at the start of the name. They’re written in alphabetical order, with the number of the carbon atom each is attached to.

Question 14

What happens with naming an organic compound when there is more than one identical side chain or functional group?

Answer 14

Use di(2), tri(3) or tetra(4) before that part of the name (but ignore this when figuring out the alphabetical order).

Question 15

What is the IUPAC system for naming organic compounds and why is it necessary?

Answer 15

It’s the agreed international la gauge of chemistry and means that scientific ideas can be communicated across the globe more effectively.

Question 16

What are the prefixes and suffixes used for the following homologous series:

1. Alkanes
2. Branches alkanes
3. Alkenes
4. Halogenoalkanes
5. Alcohols
6. Aldehydes
7. Ketones
8. Cycloalkanes
9. Carboxylic acids

Answer 16

1. -ane
2. -yl
3. -ene
4. Fluoro-/chloro-/bromo-/iodo-
5. -ol
6. -al
7. -one
8. Cyclo- -ane
9. -oic acid

Question 17

How is the unpaired electron in a radical represented?

Answer 17

As a dot.

Question 18

How is the formation of a covalent bond shown in reaction mechanisms?

Answer 18

By a curly arrow that starts from a lone electron pair or from another covalent bond.

Question 19

How is the breaking of a covalent bond shown in a reaction mechanism?

Answer 19

By a curly arrow starting from the bond.

Question 20

What is an isomer?

Answer 20

Molecules that have the same molecular formula but with the atoms arranged differently.

Question 21

What are structural isomers?

Answer 21

Structural isomers have the same molecular formulae but different structural formulae.

Question 22

State and describe the three different types of structural isomer.

Answer 22

1. Chain isomers - different arrangement of the hydrocarbon chain, such as branching.
2. Positional isomers - has the same functional groups but these are attached to the main chain at different points.
3. Functional group isomers - have the same atoms arranged into different functional groups.

Question 23

What is stereoisomerism?

Answer 23

Where two or more compounds have the same structural formulae but different arrangement of bonds in space.

Question 24

State and describe the two types of stereoisomerism.

Answer 24

1. E-Z isomerism - difference in the position of groups at either side of a carbon-carbon double bond. Groups on the same side = Z and on opposite sides = E.
2. Optical isomerism - explained in a different topic.

Question 25

Why does E-Z isomerism occur?

Answer 25

As a result of restricted rotation about the planar carbon-carbon double bond.

Question 26

What rules can be used to help determine E-Z isomerism?

Answer 26

Cahn-Ingold-Prelog (CIP) rules.

Question 27

Explain how to use the CIP rules.

Answer 27

1. Assign a priority to the two atoms attached to each carbon in a double bond.
2. To do this, look at the atoms directly bonded to each of the carbon-carbon double bond carbon atoms. The atom with the higher atomic number is given the higher priority.
3. To figure out which type of isomer is present, look at the arrangement of the two higher priority atoms.

Question 28

What do CIP rules tell you to do if the two atoms bonded directly to the carbon-carbon double bond carbon atoms are the same?

Answer 28

Look at the next atom in the groups to figure out which has the higher priority.