IB Chemistry HL - Unit 10 Organic Chemistry
Members of the same homologous series differ by (1).
(1) - CH₂
The lower the (1) of the carbon-halogen bond in a halogenoalkane, the easier it is for to undergo (2).
(1) - bond enthalpy (2) - nucleophilic substitution
The greater the (1) of the carbon-halogen bond in a halogenoalkane, the easier it is for it to undergo (2).
(1) - polarity (2) - nucleophilic substitution
Explain why benzene undergoes substitution reactions instead of addition reactions, despite being unsaturated.
- Benzene has delocalised electrons - p orbitals of carbon atoms create delocalised electron cloud → create stability, lowers internal energy
State the name of the functional group in carboxylic acids.
A carboxylic acid's functional group is carboxyl (-COOH) Prefix: -anoic acid
What is a chiral carbon?
A chiral/asymmetric carbon is bonded to 4 different substituents/groups.
Describe what is meant by a "full structural formula".
A full structural formula shows all atoms and the bonds between them.
What is a homologous series?
A homologous series is a family of organic molecules with the same functional group.
State the name of the functional group in ketones.
A ketone's functional group is carbonyl (- C = O) Prefix: -anone
State the name of the functional group in nitriles.
A nitrile's functional group is nitrile (- C ≡ N) Prefix: -anenitrile
Define what is meant by a "nucleophile".
A nucleophile is a species which is highly attracted to positive charges. Nucleophiles typically contain lone pairs of electrons.
What is a primary carbon atom?
A primary carbon atom is a carbon atom bonded to the functional group of an organic molecule and one or zero other carbon atoms.
What type of halogenoalkane is required to go through Sₙ2 nucleophilic substitution?
A primary halogenoalkane is required to go through Sₙ2 nucleophilic substitution.
What is a primary nitrogen atom?
A primary nitrogen atom is a nitrogen atom bonded to one carbon atom.
Define what is meant by a racemic mixture.
A racemic mixture is a mixture of two enantiomers in equal proportions.
What is a secondary carbon atom?
A secondary carbon atom is a carbon atom bonded to the functional group of an organic molecule and two other carbon atoms.
What is a secondary nitrogen atom?
A secondary nitrogen atom is a nitrogen atom bonded to two carbon atom.
Define what is meant by a "structural isomer".
A structural isomer is a molecule with the same molecular formula but different structural formula to another molecule.
What is a tertiary carbon atom?
A tertiary carbon atom is a carbon atom bonded to the functional group of an organic molecule and three other carbon atoms.
What type of halogenoalkane is required to go through Sₙ1 nucleophilic substitution?
A tertiary halogenoalkane is required to go through Sₙ2 nucleophilic substitution.
What is a tertiary nitrogen atom?
A tertiary nitrogen atom is a nitrogen atom bonded to three carbon atoms.
State the name of the functional group in alcohols, as well as the prefix of the compounds' names.
An alcohol's functional group is hydroxyl (-OH) Prefix: -anol
State the name of the functional group in aldehydes.
An aldehyde's functional group is aldehyde (-CHO) Prefix: -anal
State the name of the functional group in alkenes.
An alkene's functional group is alkenyl (C = C) Prefix: -ene
State the name of the functional group in alkynes.
An alkyne's functional group is alkynyl (C ≡ C) Prefix: -yne
State the name of the functional group in amides.
An amide's functional group is carboxyamide (-COONH₂) Prefix: -anamide
State the name of the functional group in amines.
An amine's functional group is amine (-NH₂) Prefix: -anamine
State the name of the functional group in arenes.
An arene's functional group is phenyl. Prefix: -benzene
Define what is meant by an "electrophile".
An electrophile is a species which is highly attracted to negative charges.
Describe the process of forming an ester.
An ester is formed between a carboxylic acid and an alcohol. A concentrated sulfuric acid (H₂SO₄) catalyst is needed.
State the name of the functional group in esters.
An ester's functional group is ester (-COO) Prefix: (alcohol prefix)-yl (carboxylic acid prefix)-anoate
State the name of the functional group in ethers.
An ether's functional group is ether (R - O - R) Prefix: (longer chain)-oxy-(shorter chain)
Define what is meant by an isomer.
An isomer is a molecule with an equal molecular formula but a different structural formula to another molecule.
When do cis-trans and E/Z isomers arise?
Cis-trans and E/Z isomers arise in cyclic and double bonded molecules.
Define what is meant by a "cis-trans isomer".
Cis-trans isomers exist where there is restricted rotation around atoms.
Define what is meant by a "configurational isomer".
Configurational isomers contains atoms/groups which can only be interconverted by breaking covalent bonds.
Describe how to determine whether an isomer is E or Z.
Determining whether an isomer is E or Z: - Compare groups at each end of double bond - Compare first atom attached to carbon - atom with higher molecular mass is prioritised - If atom is the same, compare molecular masses of next atom in chain - If highest priority groups are on opposite sides of double bond, E isomer - If highest priority groups on same side of double bond, Z isomer
Define what is meant by a "diastereomer".
Diastereomers are stereoisomers which contain different arrangements of the substituents at least one, but not all, chiral carbons.
Outline the differences between Sₙ1 and Sₙ2 nucleophilic substitution.
Differences between Sₙ1 and Sₙ2: - Sₙ1 requires a tertiary halogenoalkane, while Sₙ2 requires a primary halogenoalkane - Sₙ1 involves one species in the first step (unimolecular), Sₙ2 involves two species in the first step (bimolecular) - Sₙ1 has a carbocation intermediate phase, Sₙ2 has an anion intermediate phase - Sₙ1 requires a polar, protic solvent, while Sₙ2 requires a polar, aprotic solvent - Sₙ1 is faster than Sₙ2
Explain the two differences in properties between enantiomers of the same molecule.
Differences in enantiomer properties: 1. Optical activity: Enantiomers rotate the plane of polarization of plane polarized light → opposite enantiomers rotate plane by equal magnitude in opposite directions 2. Reactivity with chiral molecules: Different enantiomers cause chiral compounds to react differently
Outline the process of electrophilic addition in alkenes.
Electrophilic addition in alkenes: 1. Halogen molecule/Hydrogen halide approaches C=C double bond in alkene due to negative charge density 2. Electrons in C=C double bond repel electrons in bond holding halogen molecule/hydrogen halide, giving halogen molecule/hydrogen halide negative and positive charge densities 3. Heterolytic fission occurs in halogen molecule/hydrogen halide → negative region receives electrons to form negative ion (electrophile), positive region becomes positive ion 4. π bond in C=C double bond breaks, and new bond forms with positive ion → carbocation formed 5. Negatively charged ion bonds to positive carbon ion
When is electrophilic addition used?
Electrophilic addition is used to add an electrophile to alkenes.
What is an enantiomer?
Enantiomers are the two non-superimposable isomers formed from the change of arrangement of substituents on a chiral carbon. Enantiomers are mirror images of each other.
Describe the evidence for why benzene has a ring structure and does not behave like alkenes when reacting.
Evidence for benzene's ring structure: 1. C - C bond lengths in benzene are equal 2. Theoretical value for energy required hydrogenate benzene is different than experimental value 3. Benzene typically undergoes substitution reactions instead of addition reactions 4. Molecules of benzene bonded to halogens only have one isomer.
State the factors which affect rate of nucleophilic substitution reactions.
Factors affecting rate of nucleophilic substitution: 1. Mechanism (i.e. Sₙ1 faster than Sₙ2) 2. Polarity of carbon-halogen bond 3. Bond enthalpy/strength of carbon-halogen bond (Dominant over polarity of carbon-halogen bond)
Which reaction mechanism is used for halogenation of an alkane?
Free radical substitution is used for halogenation of alkane.
Give the mechanism for the reaction of methane (CH₄) and chlorine (Cl₂), and state the name of the products.
Halogenation via free radical substitution: Initiation: Cl₂ (UV light)→ 2Cl∙ Propagation: Cl∙ + CH₄ → CH₃∙+ HCl CH₃∙+ Cl₂ → CH₃Cl + Cl∙ Termination: CH₃∙ + Cl∙→ CH₃Cl
Define what is meant by "heterolytic fission".
Heterolytic fission occurs when a covalent bond between two atoms breaks, and one atom receives both electrons in the shared pair, leaving the other with none.
Define what is meant by "homolytic fission".
Homolytic fission occurs when a covalent bond between two atoms breaks, and each atom retains their shared electron.
State the product of hydrating an alkene.
Hydrating an alkene produces an alcohol.
State the catalyst and conditions needed to hydrate an alkene.
Hydration of an alkene requires sulfuric acid (H₂SO₄), steam, and a temperature >100ºC.
What does Markovnikov's rule state for electrophilic substitution?
Markovnikov's rule states that, in electrophilic substitution of a hydrogen halide, the hydrogen will bond to the carbon bonded to a greater number of preexisting hydrogens
How are monomers represented when drawn?
Monomers are represented as: n(monomer)
Explain how to name an organic compound using IUPAC rules.
Naming organic compounds: - Identify the longest carbon chain connected to the functional group → gives stem - Identify type of functional group → gives suffix - Identify side chains → gives prefix
Outline the mechanism for the nitration of benzene.
Nitration of benzene (electrophilic addition): 1. Nitric acid mixed with sulfuric acid to form nitronium ion (NO₂⁺): HNO₃ + H₂SO₄ → H₂O + NO₂⁺ + HSO₄⁻ 2. NO₂⁺ ion attracted to benzene's electron ring → Electrons move from benzene ring to NO₂⁺ ion, forming bond 3. Benzene contains carbon bonded to both hydrogen and NO₂⁺ → H⁺ ion released 4. H⁺ ion reacts with HSO₄⁻ ion to form H₂SO₄ Overall reaction: C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O Conditions: Concentrated sulfuric acid (H₂SO₄), temperature of 50ºC
When is nucleophilic substitution used?
Nucleophilic substitution is used when a halogenoalkane reacts with a nucleophile. E.g. CH₃Cl + OH⁻ → CH₃OH + Cl⁻
Define what is meant by an "optical isomer".
Optical isomers contain asymmetric (chiral) carbon atom. Optical isomers rotate the plane of plane-polarized light which they interact with.
What is the product formed if a primary alcohol is oxidised?
Oxidising a primary alcohol produces an aldehyde.
What product is formed if a primary alcohol is oxidised using reflux?
Oxidising a primary alcohol through reflux forms a carboxylic acid.
What product is formed if a secondary alcohol is oxidised?
Oxidising a secondary alcohol produces a ketone.
State two reduction agents, ranking their relative strengths.
Oxidising agents: 1. Lithium aluminum hydride (LiAlH₄) with dry ether and heat→ Strong enough to reduce a carboxylic acid to an alcohol (dangerous) 2. Sodium borohydride (NaBH₄) with heat→ Strong enough to reduce an aldehyde into an alcohol
What product is formed if an aldehyde is oxidised?
Oxidising an aldehyde produces a carboxylic acid.
Define what is meant by a "protic" solvent.
Protic solvents can form hydrogen bonds.
Outline the mechanism for the reduction of nitrobenzene.
Reduction of nitrobenzene: 1. Nitrobenzene put in mixture of tin (Sn) and concentrated hydrochloric acid (HCl) → Forms phenylammonium ions (C₆H₅(NH₃)⁺) 2. Phenylammonium reacted with sodium hydroxide → OH⁻ ion reacts with H⁺ with coordinated bond → H₂O formed, leaves phenylamine (C₆H₅NH₂)
How are repeating units represented when drawn?
Repeating units are represented as: -(monomer)-n
Define what "resolution" is regarding enantiomers.
Resolution is the process by which two separate enantiomers are removed from a racemic mixture.
Define what is meant by "retro-synthesis".
Retro-synthesis is the process by which a target molecule is reacted backwards to form precursors, until it forms the original molecule.
Define what is meant by a "stereoisomer".
Stereoisomers refer to molecules with groups/atoms in the same place, but with different spatial arrangement.
Outline the process of Sₙ1 nucleophilic substitution of a halogenoalkane.
Sₙ1 process: 1. Carbon-halogen bond undergoes heterolytic fission → halogen receives shared electron pair, forming negative halogen ion 2. Carbocation intermediate formed, nucleophile attracted to positive carbon ion 3. Nucleophile bonds to carbocation
Outline the process of Sₙ2 nucleophilic substitution of a halogenoalkane.
Sₙ2 process: 1. Nucleophile attracted to positively charged carbon atom bonded to halogen 2. Carbon-halogen bond undergoes heterolytic fission → halogen receives shared electron pair 3. Unstable anion transition state formed, both nucleophile and halogen bonded to halogenoalkane 4. Halogen bond completely breaks, bond formed between carbon atom and nucleophile
Which type of alcohol cannot be oxidised?
Tertiary alcohols cannot be oxidised.
State the name of the catalyst and the conditions used in the hydrogenation of an alkene.
The catalyst used in the hydrogenation of an alkene is Nickel (Ni). The temperature is 150ºC.
State the two possible products of incomplete combustion.
The possible products of incomplete combustion: → CO + H₂O → C + H₂O
State the products of complete combustion.
The products of complete combustion are CO₂ and H₂O.
Give the symbol for oxidation.
The symbol for oxidation is [+O]
Give the symbol for reduction.
The symbol for reduction is [+H].
