Formulae, Names and Isomers

Question 1

General formula

Answer 1

An algebraic formula that can describe any member of a family of compounds (e.g. ethene -> Alkenes: CₙH₂ₙ)

Question 2

Empirical formula

Answer 2

The simplest whole number ratio of atoms of each element in a compound (cancel the numbers down if possible) (e.g. ethene -> CH2)

Question 3

Molecular formula

Answer 3

The actual number of atoms of each element in a molecule (e.g. ethene -> C2H4)

Question 4

Displayed formula

Answer 4

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

Question 5

Structural formula

Answer 5

Shows the arrangement of atoms carbon by carbon, with the attached hydrogens and functional groups (e.g. ethene -> CH2CH2)

Question 6

Homologous series

Answer 6

A group of compounds that can all be represented by the same general formula and similar chemical properties.

Question 7

Why do compounds in a homologous series react similarly?

Answer 7

They have the same functional group.

Question 8

Functional group

Answer 8

A group of atoms that determine how a compound typically reacts

Question 9

What is the functional group of alkenes?

Answer 9

C=C (double bond)

Question 10

What is the functional group of alcohols?

Answer 10

-OH

Question 11

What is the functional group of carboxylic acids?

Answer 11

-COOH

Question 12

What is the functional group of esters?

Answer 12

-COO-

Question 13

What does “nomenclature” mean in organic chemistry?

Answer 13

The system of naming organic compounds using IUPAC rules.

Question 14

How do you determine the stem of an organic compound’s name?

Answer 14

By counting the number of carbon atoms in the main chain.

Question 15

What are the stems for 1 to 6 carbon atoms?

Answer 15

1: meth-

2: eth-

3: prop-

4: but-

5: pent-

6: hex-

Question 16

How is the main functional group indicated in a name?

Answer 16

With a prefix or suffix depending on the group.

Question 17

How do you number the carbon chain when naming?

Answer 17

So the functional group has the lowest possible number.

Question 18

What if there’s more than one of the same functional group?

Answer 18

Use di-, tri-, tetra- before the suffix (e.g. diol for two -OH groups).

Question 19

What is the IUPAC name of CH₃CH=CHCH₃?

Answer 19

But-2-ene

Question 20

What is the IUPAC name of CH₃CH₂CH₂OH?

Answer 20

Propan-1-ol

Question 21

What would a compound with two -OH groups on a 3-carbon chain be called?

Answer 21

Propanediol

Question 23

What are the three main types of isomerism in organic chemistry?

Answer 23

• Different carbon chain shapes
• Functional groups in different positions
• Different functional groups

Question 24

What is chain isomerism?

Answer 24

When carbon atoms are arranged differently (e.g. straight vs branched).

Question 25

Give an example of chain isomers.

Answer 25

Butane and methylpropane (both C₄H₁₀)

Question 26

What is positional isomerism? (different places)

Answer 26

Same functional group, but in different positions on the chain.

Question 27

Give an example of positional isomers.

Answer 27

But-1-ene and but-2-ene (both C₄H₈)

Question 28

What is functional group isomerism?

Answer 28

When the same atoms are arranged into different functional groups.

Question 29

Give an example of functional group isomers.

Answer 29

Methyl propanoate and butanoic acid (both C₄H₈O₂)