Organic chemistry: Intro

Question 1

State the 6 ways organic compounds can be represented?

Answer 1

Empirical formula, molecular formula, general formula, structural formula, displayed formula and skeletal formula

Question 2

What is a general formula?

Answer 2

Algebraic formula that can describe any member of a family of compounds e.g. CnH2n+2

Question 3

What is a empirical formula?

Answer 3

Simplest ratio of atoms of each element in a comound

Question 4

What is a molecular formula?

Answer 4

the actual number of atoms of each element in a molecule

Question 5

What is a structural formula?

Answer 5

shows the atoms carbon by carbon, with attached hydrogens and functional groups

Question 6

What is skeletal formula?

Answer 6

Shows the bonds of the carbon skeleton only with any functional group ( H and C atoms not shown)

Question 7

What is a displayed formula?

Answer 7

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

Question 8

What is a homologous series?

Answer 8

a group of compounds that contain the same functional group, can be represented by the same general formula

Question 9

What type of atoms are not counted as side chains?

Answer 9

Hydrogen

Question 10

Rules of nomenclature: Alkanes (saturated hydrocarbons) ?

Answer 10

Rule 1 : Find the longest unbroken carbon chain and use it as a root name (e.g. 5 C long would be pent)
Rule 2: Name branches alphabetically (e.g. ethyl before methyl)
Rule 3 : Number the positions of the branches (from the end of the carbon chain that gives the lowest numbers)

Question 11

Rule of nomenclature: compounds with 1 functional group

Answer 11

Rule 1 : select the longest carbon chain which contains the functional group
Rule 2 : Number the position of the functional group (from end of carbon chain that gives the lowest number)

Question 12

Name of carbon side chains

Answer 12

methyl, ethyl, propyl

Question 13

Functional groups: alcohol, halogens, aldehyde and carboxylic group and their affects on nomenclature?

Answer 13

• OH is an alcohol group and takes the suffix -anol, (UNLESS there is a more important group on the chain, in which case it becomes a hydroxy- prefix)
• Cl is a group (along with other halogens) that always becomes a prefix. (It is the lowest priority. When there are other halogens they are named in alphabetical order.)
• CHO is the aldehyde group. It becomes the -anal suffix. It is a high priority group.
• COOH is the carboxylic acid group. It has the ending -anoic acid. it is also high priority (more than aldehydes).

Question 14

What are isomers?

Answer 14

Molecules with the same molecular formula but atoms arranged differently in space

Question 15

Two types of isomers?

Answer 15

Structural isomers and stereoisomers

Question 16

What is Structural isomerism ?

Answer 16

defined as having same molecular formula but different structural formulae. there are three subdivisions: positional isomerism, functional group isomerism and chain isomerism

Question 17

Three types of isomerism sub-divisions in structural isomerism?

Answer 17

Positional, functional group and chain

Question 18

What is positional isomerism?

Answer 18

the same functional group attached to the main chain at different points
e.g. 1-chloropropane or 2-chloropropane

Question 19

What is chain isomerism?

Answer 19

Hydrocarbon chain is arranged differently

e.g. butan-1-ol and 2-methylpropan-1-ol

Question 20

What is functional group isomerism?

Answer 20

isomers contain different functional groups

Question 21

What are stereoisomers?

Answer 21

Where 2 or more compounds have the same structural formula. They differ in arrangement of the bonds in space. Two types: E-Z isomerism & Optical isomerism

Question 22

What is E/Z isomerism and how does it arise?

Answer 22

• type of stereoisomer caused by restricted rotation around double bond (C=C restricts rotation around bond)
• arises when carbon atoms are attached to different substituents

Question 23

What is priority based on when naming E/Z isomers?

Answer 23

Atomic mass of group

higher mass = higher priority

Question 24

What type of rules are used to name E/Z isomers?

Answer 24

Cahn-inglod-prelog rule (CIP rules)

Question 25

Describe method of naming compounds by cahn-ingold-prelog method

Answer 25

1 Locate the C=C and redraw so it's in the centre of the molecule (draw substituents around it) 2 Assign priorities - depends on RAM, greater RAM, the higher the priority 3 Decide if the isomer is E or Z Z (Zusammen) - if the highest priority substituents are on the same side of C=C E (Entgegen) - if highest priority groups are on different sides of the C=C e.g. Z-1-bromo-2-chloro-1-fluoroethene

Question 26

Cis is the same as what? and Trans is the same as what?

Answer 26

``` Cis = Z-isomerism Trans= E-isomerism ```

Question 27

Reactions of organic compounds can be explained using what?

Answer 27

Mechanisms

Question 28

What does the dot represent in the free radical mechanism?

Answer 28

- the unpaired electron in a radical

Question 29

What's a radical?

Answer 29

a species with unpaired electrons, makes radical highly reactive

Question 30

Series of reactions in free-radical mechanism?

Answer 30

Initiation, propagation, and termination

Question 31

What happens in initiation?

Answer 31

UV light breaks down the halogen bonds producing reactive intermediates called free radicals

Question 32

What happens in propagation?

Answer 32

a hydrogen is replaced and the Cl• radical reformed as a catalyst

Question 33

What happens in termination?

Answer 33

two radicals join to end the chain reaction and form a stable product

Question 34

What CAN happen in propagation?

Answer 34

- propagation step can continue many times to result in multiple substitutions, this is a chain reaction