Organic Chemistry

Question 1

What is a chloroalkane?

Answer 1

A Chloroalkane is a compound in which one or more of the hydrogen atoms in an alkane molecule have been replaced by chlorine atoms.

Question 2

What is the main use of chloroalkanes?

Answer 2

As solvents (e.g for removing oil and grease marks from machinery)

Question 3

Name the first four chloroalkanes.

Answer 3

monochloromethane
dichloromethane
trichloromethane
tetrachloromethane

Question 4

What is a functional group?

Answer 4

A functional group is an atom or group of atoms which is responsible for the characteristic properties of an organic compound or a series of organic compounds.

Question 5

Define a primary alcohol.

Answer 5

A primary alcohol is one where the carbon atom joined to the -OH group is attached to only one other carbon atom.

Question 6

Define a secondary alcohol.

Answer 6

A secondary alcohol is one where the carbon atom joined to the -OH group is attached to two other carbon atoms.

Question 7

Define a tertiary alcohol.

Answer 7

A tertiary alcohol is one where the carbon atom joined to the -OH group is attached to three other carbon atoms.

Question 8

Would Methanol be considered a primary, secondary or tertiary alcohol?

Answer 8

primary

Question 9

What is fermentation used for?

Answer 9

In the brewing industry to manufacture beer and cider, which have an ethanol concentration of about 4-5% v/v

Question 10

True or False, All alcohols are toxic to a greater or lesser extent.

Answer 10

True

Question 11

What does ethanol do to your body?

Answer 11

It is a drug that depresses the activity of the central nervous system.

Question 12

What are the uses of ethanol?

Answer 12

A fuel (chp 21) or a solvent

Question 13

Discuss the physical properties of alcohols in terms of boiling points.

Answer 13

Alcohols have a higher boiling point compared to the corresponding alkanes. First four alcohols are gases at room temp. The highly polar -OH

Question 14

Discuss the physical properties of alcohols in terms of boiling points.

Answer 14

Alcohols have a higher boiling point compared to the corresponding alkanes. First four alcohols are gases at room temp. Reason: The highly polar -OH group gives rise to hydrogen bonding between the alcohol molecules, therefore extra energy is needed to break these bonds.

Question 15

Discuss the physical properties of alcohols in terms of solubility.

Answer 15

Methanol, Ethanol and propan-1-ol are completely miscible with water. The solubility in water is due to hydrogen bonding between alcohol molecules and the water molecules.

Question 16

Discuss the distillation of ethanol.

Answer 16

It is impossible to separate ethanol and water by distillation as the two liquids form a mixture with a constant boiling point that distils over as a liquid (95% ethanol)

Question 17

What is another way to call pure ethanol

Answer 17

absolute alcohol

Question 18

What is a substitution reaction?

Answer 18

A substitution reaction is a chemical reaction in which an atom or a group of atoms in a molecule is replaced by another atom or group of atoms.

Question 19

What is a mechanism?

Answer 19

The mechanism of a reaction is the detailed step-by-step description of how the overall reaction occurs.

Question 20

What is a chain reaction?

Answer 20

A chain reaction is a reaction that continues on and on because a product from one step of the reaction is a reactant for another step of the reaction.

Question 21

What lead compound increases the rate of reaction?

Answer 21

Tetraethyl lead / Pb(C2H5)4

Question 22

Define an addition reaction.

Answer 22

An addition reaction is one in which two or more molecules react together to form a single molecule.

Question 23

Describe the Ionic Addition Mechanism

Answer 23

1. Polarisation
   C2H4 + Br2
   Br2 is non polar.(If HCl it is Polar)
   The double bond in C2H4 has 4 e- shared so it is highly negative. The highly negative region causes Br2 to become (if HCl, more) polarised. (Delta + and Delta -)
2. Heterolythic Fission
   The polarisation of Br2 becomes so great that Br2 splits into two ions. (use one headed arrows to symbolise the splitting)
   Br* - *Br = Br+ + **Br-
3. Carbonium Ion Formation
   Br+ is attracted to the highly negative region (C=C)
   Forms a bond with 1C, taking an e- from another C and creating a Carbonium Ion
4. Ionic Addition
   The Carbonium Ion and Br- ion from 2. attract and join to for 1,2-dibromoethane.

Question 24

Discuss the evidence for the Ionic Addition Mechanism.

Answer 24

Add the Br2 in a solution of NaCl to C2H5 when the Carbonium Ions form, other ions along with Br- are attracted to it.
e.g Cl- from the NaCl make 1-bromo-2-chloroethane
OH- from the solution of NaCl (any solution means in water) make 2-bromoethanol

Question 25

What is the General Formula for Alcohols?

Answer 25

Cn H2n+1 OH

Question 26

What type of bond does a Carbon molecule have in a Planar Carbon Compound

Answer 26

A multiple Bond

Question 27

Are Aldehydes Polar or Non-Polar? If they are polar, what two atoms share the polar bond?

Answer 27

Polar | Carbon and Oxygen share a double bond

Question 28

What is a use of Propanone?

Answer 28

As solvents e.g Nail Polish remover

Question 29

True or False. | Ketones and aldehydes are structural isomers

Answer 29

True

Question 30

What boiling point does ethanal and ethanol have?

Answer 30

``` ethanal= 21 C ethanol= 78 C ```

Question 31

What forces of attraction are found in the following: 1. Alcohols 2. Ketones 3. Aldehydes 4. Alkanes

Answer 31

1. Hydrogen Bonding 2. Dipole-Dipole forces 3. Dipole-Dipole forces 4. Van Der Waal Forces

Question 32

Which of the following have the highest boiling point? | Alcohols, Ketones, Aldehydes, Alkanes

Answer 32

Order of descending boiling points: Alcohols Aldehydes and Ketones Alkanes

Question 33

What is an elimination reaction?

Answer 33

An Elimination reaction is one in which a small molecule is removed from a larger molecule to leave a double bond in the larger molecule. e.g ethanol -> ethene + water

Question 34

What is another name for an elimination reaction when water is removed?

Answer 34

A dehydration reaction

Question 35

What are the key features of a Carboxylic acid?

Answer 35

carbonyl and hydroxyl group

Question 36

What organic compound is found in the stings of nettles and ants?

Answer 36

Methanoic acid

Question 37

What is ethanoic acid used for?

Answer 37

To make cellulose acetate (which is used in nail varnishes and lacquers)

Question 38

Name the Organic compound that inhibits the growth of mould and is used as a food perservative

Answer 38

Propanoic acid

Question 39

What is Benzoic acid use for?

Answer 39

Food preservatives, antiseptic medicines, fungicide for treating skin problems such as ringworm and athlete's foot.

Question 40

Discuss the odours in relation to Carboxylic Acids.

Answer 40

The longer-chain carboxylic acids have unpleasant odours.

Question 41

What organic compound smells of rancid butter?

Answer 41

Butanoic acid

Question 42

What organic compound smells of human sweat?

Answer 42

Various carboxylic acids

Question 43

What organic compound causes the stench of goats?

Answer 43

Decanoic acid

Question 44

What happens to ethanoic acid after the temperature falls below T degrees celsius. What temperature is T?

Answer 44

It becomes a solid called glacial acetic acid. | T=17 C

Question 45

Explain what a dimer is.

Answer 45

the molecule group together to form pairs of molecules called dimers which are held together by hydrogen bonds. This occurs in Carboxylic Acids.

Question 46

What is the boiling point of ethanoic acid?

Answer 46

118 C

Question 47

Discuss the solubility of carboxylic acids

Answer 47

All carboxylic acids are completely soluble in water due to their ability to form hydrogen bonds with water molecules.

Question 48

What is a condensation reaction?

Answer 48

A condensation reaction is a chemical reaction in which two molecules combine to form a larger molecule with the loss of a smaller molecule such as water.

Question 49

What is a condensation reaction an example of?

Answer 49

Esterification reaction

Question 50

Name a suitable oxidising agent that can be used to turn a priamary alcohol into an aldehyde or an aldehyde into a carboxylic acid

Answer 50

Acidified sodium dichromate | Na2Cr2O7/H+

Question 51

Where does the word aldehyde come from?

Answer 51

ALcohol DEHYDrogenation

Question 52

In the presence of what can ketones and aldehydes be reduced back to alcohols?

Answer 52

hydrogen and a nickel catalyst | H2/Ni

Question 53

Ionic Substitution Mechanism

Answer 53

1.Inititation Cl* - *Cl UV light causes the bond in Cl2 to break (photolythic fission) Homolythic fission as it forms 2 Chloro free radicals (include the one headed arrows) 2.Propagation A Chloro free radical attacks a methane molecule and takes a H Cl* + CH4 = HCl + *CH3 (methyl free radical) 3.Propagation a methyl free radical attacks a chlorine molecule (Cl2) and takes a Cl forming monochloromethane and a chloro free radical *CH3 + Cl-Cl = CH3Cl + *Cl A Chain reaction is step up between steps 2 and 3 ``` 4. Termination only terminate when all free radicals are used up 1. Cl* + Cl* -> Cl2 2. Cl* + *CH3 -> CH3Cl *CH3 + *CH3. -> C2H6 (ethane) ```

Question 54

What is another way of saying the Ionic substitution mechanism

Answer 54

The Monochlorination of Methane

Question 55

Discuss the physical properties of Chloroalkanes.

Answer 55

The carbon-chloride bond in a chloroalkane has some polarity but not enough to allow the chloroalkanes to dissolve in water

Question 56

What carbon compound is formed easily from materials of plant or animal origins and contributes to the greenhouse effect that causes global warming?

Answer 56

Methane (CH4)