Introduction to Organic Chemistry

Question 1

Define empirical formula

Answer 1

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

Question 2

Define molecular formula

Answer 2

The actual number of atoms of each element in a compound.

Question 3

Define homologous series.

Answer 3

A family of organic compounds that have the same functional group. They have the same general formula and similar chemical properties.

Question 4

What so consecutive members of a homologous series differ by?

Answer 4

-CH2-

Question 5

In a homologous series, the length of the carbon chain changes. What effects does this have on the chemical or physical properties of the molecule?

Answer 5

• Has little effect on the chemical reactivity.

- Increasing C chain length increases the melting and boiling points and decreases solubility because the IMFs increase.

Question 6

Why does chain branching reduce melting points?

Answer 6

Because the molecules can’t pack together as closely.

Question 7

What is the general formula for alkanes?

Answer 7

CnH2n+2

Question 8

What is the general formula for alkenes?

Answer 8

CnH2n

Question 9

What is the general formula for alcohols?

Answer 9

CnH2n+1OH

Question 10

What is the general formula for cycloalkanes?

Answer 10

CnH2n

Question 11

What is the general formula for branched alkanes?

Answer 11

CnH2n+2

Question 12

What is the general formula for aldehydes?

Answer 12

R-CHO, where R is an alkyl group or H atom

Question 13

What is the general formula for ketones?

Answer 13

R-C=O-R’

Where R and R’ are alkyl groups (may or may not be the same), NOT an H atoms because that would make it an aldehyde

Question 14

What is the general formula for carboxylic acids?

Answer 14

R-COOH

R= alkyl group or H atom

Question 15

Define functional group

Answer 15

An atom or group of atoms in an organic molecule which is responsible for the characteristic reactions of that molecule.

Question 16

Define structural isomers.

Answer 16

Molecules with the same molecular formula, but a different structural formula

Question 17

What are the 3 different types of structural isomers?

Answer 17

1. Chain isomers- different arrangement of carbon skeleton
2. Position isomers-the position of the functional group on the carbon chain changes
3. Functional group isomers- same atoms are arranged into different functional groups

Question 18

Define stereoisomers

Answer 18

Molecules with the same structural formula, but a different arrangement of atoms in space

Question 19

what type of isomerism is E/Z isomerism?

Answer 19

Stereoisomerism

Question 20

Give 2 types of stereoisomerism

Answer 20

• E/Z

- Optical

Question 21

What is the shape of a C=C bond and the atoms bonded to this C?

Answer 21

Planar, 120 degrees bond angle

Question 22

Why does E/Z isomerism occur?

Answer 22

As a result of restricted rotation about the planar C=C double bond.

Question 23

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

Answer 23

• Assign a priority to the 2 atoms attached to each side of the double bond.
• Atom with the higher atomic number on each carbon is given the higher priority
• If the atoms directly bonded to each carbon are the same, then you look at the next atom in the groups to work out which has the higher priority
• To work out which isomer you have, look at how the two highest priority groups are arranged. If they’re positioned across the double bond from each other, it’s the E isomer. Is they’re both above or below the double bond, it’s the Z isomer.