introduction to organic chemistry part 1...introduction to organic chemistry part 1 –answerit 9....

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Introduction to Organic ChemistryPart 1

• Nomenclature

Introduction to Organic Chemistry part 1 – AnswerIT

1. What do all organic compounds contain?Carbon

2. State the link between the number of carbon atoms in a hydrocarbon chain and melting points.The larger the number of carbon atoms, the higher the melting point.

3. How are organic compounds classified?Organic molecules are classified by the dominant functional group on the molecule.

4. What is the displayed formula of a compound?All covalent bonds between all atoms are shown.


5. What is the structural formula of a compound?No covalent bonds are shown. The minimal detail using conventional groups , for an unclear structure.

6. What is the skeletal formula of a compound?Simplified organic compound formula by removing carbon and hydrogen atoms from straight chain and alkyl chains, leaving just a carbon skeleton and associated functional groups.

7. What does the molecular formula tell us about a compound?It shows the actual number of each atoms of each element present in the molecule of the compound but not the structure of the molecule.

8. What is meant by the term ‘empirical formula’?The simplest whole number ratio of the number of atoms of each element in a substance.


9. Define the term ‘homologous series’.A homologous series is a series of organic compounds which have the same functional group and similar chemical properties , but in which the formula of each successive member increases by -CH2.

10. What is the general molecular formula for an alcohol?CnH2n+2O


11. Complete the table to show the prefixes used to name hydrocarbon chains of different lengths.

Number of carbonatoms

Prefix used

1 Meth-

2 Eth-

3 Prop-

4 But-

5 Pent-

6 Hex-


12. What is the ending used to denote that a hydrocarbon is an alkane?-ane

13. What is the ending used to denote that a hydrocarbon is an alkene?-ene

14. How are halogenoalkanes named?Using the prefix fluoro, chloro-, bromo- or iodo-with the suffix ending -ane.


15. Complete the table to show the prefixes used for branched chains.

Branch Prefix used

Methyl

Ethyl

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Introduction to Organic ChemistryPart 2

• Reaction mechanisms• Isomerism

Introduction to Organic Chemistry part 2 – QuestionIT

1. What is a free radical?Very reactive species with single unpaired electron.

2. How is an unpaired electron represented in a mechanism?Single dot next to or above the species.

3. What does a curly arrow show?The movement of electron(s).

4. What is the different between a full arrow head and a single line arrow head?Full arrow = 2 electrons; single line arrow head = 1 electron.

5. Where must a curly arrow come from?Lone electron pair or bond.

6. Where must a curly arrow go?To where the new bond is formed/ where the electron is going.


7. How is the formation of a covalent bond shown in a mechanism?Curly arrow starting from a lone pair or another covalent bond, going to where the new bond is formed.

8. How is the breaking of a covalent bond shown in a mechanism?Curly arrow starting from the bond going to where the electron(s) are moving to.

9. What are the three stages of a free radical mechanism?Initiation, propagation and termination.

10. What is an isomer?Isomers are molecules which have the same molecular formula but different structural formula.

11. What are the 3 types of structural isomerism?Positional, chain, functional group.


12. What are positional isomers?Molecules with the same molecular formula but which have the functional group on different positions.

13. What are chain isomers?Molecules with the same molecular formula but a different arrangement of carbon atoms in the carbon skeleton . Similar chemical properties but slightly different physical properties(more branching = lower boiling point).

14. What are stereoisomers?Molecules with the same structural formula but a different spatial arrangement of atoms.


14. What is E-Z isomerism?If both carbon atoms on either side of the bond are attached to two different groups, then two different structures arise which cannot be interconverted.

15. How can a chemist distinguish between isomers?Isomers differ slightly in their melting and boiling points so these can be used.

16. Why does E-Z isomerism exist?It is not possible to rotate a π-bond about its axis without breaking the bonds. There is therefore restricted rotation about the double bond.

17. What is a π-bondTwo p-orbitals overlap above and below the internuclear axis.

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Alkanes and halogenoalkanesPart 1

• Fractional distillation and cracking

• Combustion of alkanes

Alkanes and Halogenoalkanes part 1 – QuestionIT

1. What is crude oil?A mixture of hydrocarbons.

2. What is the name of the process by which crude oil is separated into its different components?Fractional distillation.

3. How is separation of crude oil achieved?The larger hydrocarbons, with higher boiling points, will condense first and be tapped off near the base of the column. The smaller hydrocarbons, with smaller boiling points, will condense later and be tapped off near the top of the column.

4. What type of catalyst is used in catalytic cracking?Zeolite catalyst.


5. What are fractions?Fractions are mixtures of hydrocarbons with similar boiling points.

6. What is cracking?The process by which larger fractions can be broken up into smaller fractions.

7. What are the conditions needed for thermal cracking?High temperature (500 – 900oC) and a high pressure (70 atmospheres).

8. What are the conditions needed for catalytic cracking?Temperature which is lower than in thermal cracking (400-500 oC,), a slight pressure (slightly greater than 1 atmosphere), and a catalyst.


9. What is a fuel?A fuel is a something that can be changed in a reacting vessel to produce useful energy.

10. What are the products when a hydrocarbon is burned in excess oxygen?Water and carbon dioxide.

11. What type of reaction is burning a fuel?Combustion (exothermic)

12. Why does carbon dioxide cause global warming?Carbon dioxide prevents the earth’s heat from escaping into space which results in an increase in the earth’s temperature.


13. What are the products of incomplete combustion?Carbon monoxide or carbon and water.

14. Why does sulfur dioxide pose a threat to the environment?It dissolves in rainwater forming acid rain. This causes various problems, including erosion of buildings and statues, killing of plants and trees, and killing of fish through contamination of lakes.

15. Why are nitrogen oxides a threat to the environment?Nitrogen oxides can combine with unburned hydrocarbons to produce a photochemical smog.


16. What is flue gas desulphurisation?The alkaline materials such as lime (calcium oxide) in factory chimneys absorb acidic gases such as SO2 and prevent them from escaping.

17. What is the gypsum, made from flue gas desulphurisation, used for?Plaster.

18. What is the role of catalytic converters in car exhausts?They convert the more harmful gases present in car exhausts into less harmful ones.

AnswersAlkanes and halogenoalkanesPart 2

• Chlorination of alkanes• Nucleophilic substitution• Elimination• Ozone depletion


1. What is a substitution reaction?A substitution reaction is one in which one atom or group of atoms on the organic molecule is directly replaced by another.

2. What is a free radical?A free radical is a species which contains an unpaired electron.

3. What is homolytic fission?Homolytic fission is the breaking of a covalent bond in such a way that one electron goes to each atom.

4. What conditions are needed for homolytic fission?Ultra-violet light


5. What is Initiation?When a halogen molecule breaks up in the presence of ultra-violet light.

6. What is propagation?Propagation is the reaction of a free radical with a molecule to produce another free radical.

7. What is termination?Termination is the combination of two free radicals to form a single molecule.

8. Why are only a small number of halogen molecules needed for free radical substitution?The halogen radicals are recycled during the propagation steps.


9. Why can further propagation happen?Further propagation steps are likely if excess halogen is used.

10. How could you ensure that the halogenoalkane is the main product of free radical substitution?Use excess methane or alkane.

11. What is a nucleophile?A nucleophile is a species with a lone pair of electrons which it can use to form dative covalent bond with an electropositive carbon atom on an organic molecule.


12. What is an elimination reaction?An elimination reaction is one in which the organic molecule loses two species from adjacent carbon atoms without replacement, resulting in the formation of a double bond between the two carbon atoms.

13. What conditions are required for the nucleophilic substitution reaction to produce alcohols?Halogenoalkane heat under reflux with aqueous NaOH or aqueous KOH.

14. What conditions are required for the nucleophilic substitution reaction to produce nitriles? Halogenoalkane boiled under reflux with KCN in aqueous ethanol.


15. What conditions are required for the nucleophilic substitution reaction to produce primary amines?Halogenoalkane heated with concentrated ammonia in ethanol in a sealed tube.

16. What conditions are required for the elimination reaction to produce alkenes?Halogenoalkane boiled with a solution of KOH in ethanol. Distillation apparatus is used.

17. Explain why the carbon-halogen enthalpy influences the rate of reaction.Reactions are quicker as you descend Group VII as the C-X bonds become weaker due to weaker bond enthalpy and longer covalent bonds.


18. What are chlorofluorocarbons?Chlorofluorocarbons are halogenoalkanes containing chlorine and fluorine atoms but not hydrogen atoms, eg CCl2F2 or CClF3.

19. What happens to chlorofluorocarbons in ultra-violet light?They can undergo homolytic fission to produce free radicals.

20. What is ozone and what role does it play in the Earth’s atmosphere?Ozone (O3) is a naturally occurring substance found in the upper atmosphere. It absorbs ultra-violet radiation from the sun and prevents it from getting to the earth’s surface.

21. Recall the equations for the reaction between Cl. and O3.Cl. + O3 ClO. + O2 and ClO. + O3 2O2 + Cl.

introduction to organic chemistry part 1...introduction to organic chemistry part 1 –answerit 9....

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