Basic Organic

Question 1

What are halogenoalkanes?

Answer 1

An alkane where at least one hydrogen has been substituted by a halogen

Question 2

What is a:

• Primary halogenoalkane
• Secondary halogenoalkane
• Tertiary halogenoalkane

Answer 2

• The halogen is bonded to a carbon bonded to 1/2/3 carbons

Question 3

What are some properties of halogenoalkanes?

Answer 3

• As chain length increases, the strength of the induced dipole dipole forces increases and mp increases (not dipole dipole)
• Halogenoalkanes are polar molecules due to the differing electronegativities between the carbon and the halogen
• C-H bonds are non-polar

Question 4

What increases the strength of idd?

Answer 4

• Number of electrons
• Points of surface contact

Question 5

Why are halogenoalkanes only slightly soluble at best despite being polar molecules?

Answer 5

• The strength of the idd and the dd are not stronger than the hydrogen bonds which have to be broken to make way for these interactions

Question 6

What is a nucleophile?

Answer 6

An electron pair donor

Question 7

What is a reagent?

Answer 7

A physical substance added to a system

Question 8

What reagents are used for nucleophilic substitution of halogenoalkanes to produce alcohols?

Answer 8

NaOH, KOH Dissolved in water to release ions (aq)

Question 9

Why can halogenoalkanes take part in nucleophilic substitution?

Answer 9

The halogen is more electronegative than the carbon causing a polar bond which can act as an electrophile for a nucleophile.

Question 10

What reagents are required for nucleophilic substitution of halogenoalkanes to produce alkanenitriles?

Answer 10

NaCN, KCN dissolved in liquid ethanol.

This is because if NaCN dissolves in water, it could produce OH instead of CN and forming an alcohol rather than alkanenitriles.

Question 11

Which halogenoalkane undergoes nucleophilic substitution fastest?

Answer 11

C-I lowest bond enthalpy, lower activation energy, increased fsc

C-F highest electronegativity differences, right orientation, increased fsc

Determined by bond enthalpy

Question 12

How to measure rate of nucleophilic substitutions in halogenoalkanes?

Answer 12

To measure the reactivity of halogenoalkanes, we first dissolve the halogenoalkane in
ethanol. Then, we add
water and AgNO3 and measure how long it takes a precipitate to form.

Question 13

What is a free radical?

Answer 13

A reactive species with an unpaired electron

Question 14

How to produce a halogenoalkane?

Answer 14

Addition reaction

Free radical substitution

Question 15

What does heterolytic fission result in?

Answer 15

Ions

Question 16

What does homolytic fission result in?
What conditions required?

Answer 16

Free radicals
Heat

Temp > 450
UV Light (more energy)

Question 17

Why does the carbon-halogen bond enthalpy decrease down the group?

Question 18

What do uncontrollable side reactions do/ multiple substitution?

How to limit the effects of this?

Answer 18

• Increased time taken to produce desired products
• Decrease percentage yield
• Same atom economy
• Use excess reactant (alkane) rather than excess halogen

Question 19

What is a CFC?
What are they used for?

Answer 19

Chlorofluorocarbon
Refrigerants
Aerosol

Question 20

What is a homologous series and what are some features of it?

Answer 20

• Families of organic compounds with the same functional group and same general formula
• Differ by CH2
• Same chemical properties
• Gradual change in physical properties

Question 21

What are structural isomers?

What are the types?

Answer 21

Compounds with the same molecular formula but different structural formula

• Chain isomers
• Position isomers
• Functional group isomerism (e.g aldehydes and ketones)

Question 22

What does a double headed curly arrow show?

Answer 22

Movement of a pair of electrons

Question 23

Why does the melting point of alkanes increase as chain length increases?

Answer 23

There are more electrons and points of surface contact which increases the strength of induced dipole dipole interactions, meaning more energy is required to overcome the bonds between molecules.

Question 24

Why do alkanes how low reactivity?

Answer 24

• High bond enthalpies of C-C bond
• Low polarity of C-H (not attractive to nucleophiles/electrophiles)

Question 25

What is cracking?

Answer 25

Conversion of long-chain hydrocarbons to short-chain hydrocarbons (alkanes, alkenes and hydrogen)

Question 26

Why are pi bonds so susceptible to electrophilic attack?

Answer 26

They are exposed and have high electron density

Question 27

What is stereoisomerism?

Answer 27

When compounds have the same structural formula but different arrangements of atoms/groups in space

Question 28

When does E-Z stereoisomerism arise?

Answer 28

• Restricted rotation around the C - C double bond
• There are different groups attached to the carbon atoms
• C-C single bonds can rotate

Question 29

What is cis- trans isomerism?

Answer 29

A type of stereoisomerism where two of the groups are the same

Question 30

How does E-Z isomerism have an effect on physical properties e.g boiling point?

Answer 30

If a molecule is cis, it can be polar meaning that it also has pdd and idd. If a molecule is trans, the polarity could cancel out meaning it only has idd forces.

Question 31

Addition Reactions of Alkenes:

+ Hydrogen

Reagents:
Catalyst:
Type of Reaction:

Answer 31

• Hydrogen
• Nickel
• Addition/ Reduction

Question 32

Electrophilic Addition Reactions of Alkenes:

+ Halogens

Reagents:
Type of Fission:
Product:

Answer 32

• Halogen (no UV- not homolytic)
• Heterolytic
• Dihaloalkane

Question 33

Electrophilic Addition Reactions of Alkenes:

+