3.3.1 Intro to organic chemistry

Question 1

What is a general formula?

Answer 1

An algerbraic formula that can describe any member of a family of compounds - e.g. C_nH_2n+1OH (for all alcohols)

Question 2

What is an empirical formula?

Answer 2

The simplest ratio of atoms of each element in a compound - e.g. so ethane, C₂H₆, has the empircal formula CH₃

Question 3

What is molecular formula?

Answer 3

The actual number of atoms each element in a molecule - e.g. C₆H₁₂O₆

Question 4

What is structural formula?

Answer 4

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

Question 5

What is skeletal formula?

Answer 5

Shows the bonds of the carbon skeleton only, with any functional groups. The hydrogen and carbon atoms aren’t shown. This is handy for drawing large complicated structures, like cyclic hydrocarbons

Question 6

What is displayed formula?

Answer 6

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

Question 7

What is a homologous series?

Answer 7

A group of compounds that contain the same functional group. The can all be represented by the same general formula

Question 8

What is a functional group?

Answer 8

The reactive part of a molecule, it gives most of its chemical properties

Question 9

Give the rules of nomanclature

Answer 9

1. Count the longest continuous chain that contains the functional group - this give you the stem - e.g. 1 = meth-, 4 = but-
2. The main functional group of the molecules usually gives you the suffix - e.g. ol for alcohols
3. 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
4. Write the carbon number that the functional group is on before the suffix e.g. -2-ol
5. Any side chains or less important functional groups are added as prefixes at the start of the name, put them in alphabetical order, with the number of the carbon each is attached to
6. If there’s more than one identical side-chain or functional group, use di (2), tri (3), or tetra (4) before that part of the name - but ignore this when working out the alphabetical order

Question 10

What are isomers?

Answer 10

Two molecules are isomers of one another is they have the same molecular formula but atoms are arranged differently.

Question 11

What are structural isomers?

Answer 11

Isomers with a different structural arrangment of atoms, the atoms are connected in different ways.

They have the same molecular formula but a different structural formula

Question 12

What is a chain isomer?

Answer 12

Chain isomers have different arrangements of the carbon skeleton. Some straight chains and others branched in different ways - e.g butane and methyl propane

Question 13

What is a positional isomer?

Answer 13

Positional isomers have the same carbon skeleton and the same atoms or groups of atoms attached, the difference is that** the atom, or group of atoms is attached to different carbons ** - e.g. 1-chlorobutane and 2-chlorobutane

Question 14

What is a functional group isomer?

Answer 14

Functional group isomers have the same atoms arranged into different functional groups - e.g. Hex-1-ene and Cyclo =hexane

Question 15

What are stereoisomers?

Answer 15

Stereoisomers have the same structural formula but a different arrangement in space

Question 16

Why do stereoisomer exist?

Answer 16

Double bonds can’t rotate

1. Carbon atoms in a C=C double bond and atoms bonded to theses carbons all lie in the same plane
2. Atoms around C=C double bonds cannot rotate around them like they can around single bonds
3. The restricted roation around the C=C double bond causes a type of stereoisomerism called E/Z isomerism

Question 17

What is a Z isomer?

Answer 17

Has the same group both above or both bellow the double bond

Question 18

What is an E isomer?

Answer 18

Has the same group positioned across the double bond

Question 19

How does E/Z isomerism work when there are 3 or 4 different groups instead of 2?

Answer 19

Cahn-Ingold-Prelog (CIP) priority rules are used.

1. Assign a priority to the two atoms attached to each side in the double bond, the atom with the higher atomic number on each carbon is given priority - e.g. F has an atomic number of 9 and H has an atomic number of 1 so F has priority
2. Observe how the two higher priority groups are arranged

If atoms directly bonded to the carbon are the same then the next atom down the group determines the higher priority