CAPE Chemistry Module 1: 2022-2011

State the reagents and condition for the reaction (2022)

NaCN/HCl, room temperature

State the reagents and conditions for the reaction (2022)

H+/potassium dichromate, heat

State the name of compound D (2022)

propanoyl chloride

State the name of compound E (2022)

propanoyl chloride

Account for the fact that pKb of phenylamine is greater than ethylamine (2022)

* higher pKb indicating a weaker base.
* ethylamine is stronger base than phenylamine
* electron-withdrawing effect of the phenyl group in phenylamine → decreased availability of the lone pair of nitrogen atom to act as a proton acceptor; reducing its electron density
* ethylamine lacks this electron-withdrawing group→ lone pair of electrons on the nitrogen atom is more available for protonation

State the name of monomer involved and type of polymerization (2022)

prop-2-ene

Addition polymerization

State the type of polymerization and the monomers involved (2022)

* 1,2-dimetyleth-1,2-diol and
* condensation polymerzation

identify a compound which in aqueous solution wil break down polymer Q but not polymer P (2022)

* HCl
* H2SO4
* NaOH

define structural isomerism (2021)

same molecular formula but different structural formula (connection of atoms)

Define each type of structural isomerism (2021)

* Chain isomerism: carbon skeleton of the molecule differs between isomers
* Position isomerism: the functional group or substituent on the carbon chain is located at different positions in the molecule.
* Functional group isomerism: molecules have different functional groups, leading to different chemical properties.

State the reaction mechanism for: halogenation of alkane (2021)

Free Radical substitution.

State the reaction mechanism for alkene + HBr (2021)

electrophilic addition

Describe the observation of: aqueous bromine + pentane in sunlight (2021)

red/brown to colourless; Br decolorizes

Describe the observation of: aqueous bromine + pentane without sunlight (2021)

remains brown; no reaction

Describe the observation of: cold acidified potassium manganate + pentane (2021)

purple to colourless

State the reaction mechanism and type of reaction for halohexane + NaOH → alcohol. (2019)

Mechanism: nucleophilic substitution

type: oxidation reaction

State reagents and conditions for nitration of benzene (2019)

REAGENTS: conc H2SO4, conc HNO3

CONDITION: 50C

Outline the mechanism of benzene to nitrobenzene (2019)

* Mechanism: electrophilic substitution
* Generate NO2 (nitronium) by taking H from H2SO4 and releasing water
* Attack of nitronium by benzene pi bond.
* H on benzene removed by OHSO3
* nitrobenzene formed; H2SO4 reformed

State the Reagents and conditions of reduction of nitrobenzene (2019)

REAGENTS: Sn/HCl

CONDITIONS: reflux, heat

State reagents and conditions for diazotization (2019)

Reagents: NaNO2, HCl

Conditions: 0-5C

State reagents, condition and name of reaction (2019)

Name of reaction: Coupling (with Diazonium Salt)

Reagents: NaOH

Conditions: 0-5C

Name the class of compounds, and a use (2019)

azo compounds, used as dyes

Using ethylamine, explain “All amines are weak bases, and aqueous solutions of amines are basic” (2019)

* Amines have a lone pair of electrons on the nitrogen atom
* lone pair allows accepting of proton

The pKb values of ethanamide, ethylamine, and phenylamine are 14.51, 3.27 and 9.38. Account for the differences (2019) \[4mks\]

* ethanamide (14.51) is weakest base
* ethylamine is strongest base
* phenylamine is middle
* smaller the pKb, the stronger the base

\
*Ethanamide*

* has a carbonyl group (C=O) attached to the nitrogen atom.
* C=O, electron-withdrawing group, reduces the availability of the lone pair of electrons on the nitrogen atom
* resonance stabilization of the C=O bond; delocalizes the electron density away from the nitrogen atom.

\
*Ethylamine*

* ethyl group attached to the nitrogen atom
* electron-donating group increases the availability of the lone pair of electrons on the nitrogen atom

\
*Phenylamine*

* phenyl group attached to the nitrogen atom
* electron-donating group and increases the availability of the lone pair of electrons on the nitrogen atom
* some e- delocalizes around benzene ring

State the reagents and observation for phenol to sodium phenoxiate ion (2019)

REAGENTS: NaOH

OBSERVATION: raise in temp

State reagents and observations for phenol to following compound(2019)

REAGENTS: aqueous Bromine

OBSERVATIONS: brown to colourless; white ppt

State reagent for phenol to organic ester

acyl halide ( acid halide )

State the reaction mechanism for B to occur, and the class of compounds to which B belongs. Note A: 3-methylpent-2-ene (2019)

Mechanism: electrophilic addition

B: haloalkane

Given that compound B is 3-bromo-3methylpentane, identify the reaction mechanism leading to C. Also identify the class of compounds that C belongs (2019)

Mechanism: nucleophilic substitution

C: alcohols

State 3 characteristics of homologous series (2017(

* Same functional group
* Similar chemical properties
* Gradation in physical properties: Members of a homologous series exhibit a gradation in their physical properties such as boiling points, melting points, density, and solubility. This is because as the molecular weight increases, the intermolecular forces between the molecules also increase.
* Same general formula
* Increase in molecular size: Compounds in a homologous series have a gradual increase in molecular size as the number of carbon atoms in the molecule increases.

Describe an experiment to distinguish between the compound(2017)

Reaction with bromine:

Benzene: remains brown

cyclic hexene: brown to colourless.

State the type of reaction, reagents and conditions

Type: Bromination/Halogenation

Reagents: Br2

Condition: Fe3+ or Al3+ catalyst

State observation of carboxylic acid + SOCl2, and the products (2014)

PRODUCTS: acid chloride, SO2, HCl

OBSERVATIONS:

* bubbling and heat generation
* pungent smell from HCl
* colourless to yellow

State the observations of C-I bond and silver nitrate (2014)

* yellow ppt (of AgI)

State observation of bromination of phenol (2014)

* brown to colourless

State observation of halogentaion( bromine) of alkene (2014)

* brown to colourless

State the reaction mechanism for bromoalkane refluxed in aqueous sodium hydroxide. (2014)

nucleophilic substitution

State the products, mechanism of bromoalkane refluxed in NaOH (2014)

PRODUCTS: alcohol and NaBr

Mechanism: nucleophilic substitution

State the products of P, type of reaction and a use of the non-alcoholic product (2013)

Type of Reaction: Alkaline Hydrolysis (Saponification)

Products: glycerol \[ C3H5(OH)3 \], soap (acid salt)

Use of soap: cleaning purposes

State the products of P, the type of reaction and a use of the non-alcoholic product formed. (2013)

Type of Reaction: transesterification

Products: acyl ester and glycerol

Use of acyl ester: biodiesel

State the reagent to form the product below (2013)

Reagent: acyl halide \[ halogenated carbonyls \],

State the reagents, conditions, type and mechanism of reaction. (2013)

Reagents: conc H2SO4. conc HNO3

Conditions: 50C

Type: substitution or nitration

Mechanism: electrophilic substitution

State the reagents, conditions, type and mechanism of reaction. (2013)

Reagents: Br2

Conditions: Fe3+ or Al3+ catalyst

Type: substitution or nitration

Mechanism: electrophilic substitution

State the reagents, conditions and type of reaction. (2013)

Reagents: Sn/conc HCl, treated w/ NaOH

Conditions: heat, reflux

Type: reduction

Arrange benzene, methylbenzene and nitrobenzene in order of reactivity with halogen. Justify your answer. (2013)

ORDER: methylbenzene > benzene > nitrobenzene

\
*methylbenzene*

* presence of a methyl group (-CH3) which is an electron-donating group.
* methyl group increases the electron density of the ring
* makes it more nucleophilic

\
*benzene*

* presence of only the delocalized pi-electrons

\
*nitrobenzene*

* nitro group (-NO2) is an electron-withdrawing group
* nitro group reduces the electron density of the ring
* less nucleophilic and less reactive

State the class of compounds formed with cold & hot H+/KMnO4 (2013)

Cold: alcohol (diol)

Hot: methanal → methanoic acid → CO2 + H2O

State the reaction mechanism for compound + NaOH (2011)

nucleophilic substitution

State the reagents and condition used. (2011)

conc H2SO4, 180C

State the reagents and conditions (2011)

REAGENTS: conc H2SO4, water

CONDITIONS: heat

State the reagent and type of reaction.

REAGENT: any oxidizing agent

Type: Oxidation

Explain the difference in acidity of alcohols, phenol and carboxylic acids. (Include acid strength, inductive and conjugative effects ) (2011) \[5mks\]

*Alcohols*

* weak acidity
* oxygen atom in the hydroxyl group is highly electronegative
* C-O bond is polarized towards oxygen.
* The oxygen atom withdraw electron density from the carbon atom through inductive effects, which weakens the O-H bond and makes it less acidic.

*Phenols*

* more acidic than alcohols
* hydroxyl group is directly attached to an aromatic ring, which stabilizes the resulting phenoxide anion through resonance.
* The phenoxide anion has a delocalized negative charge over the aromatic ring
* The presence of the aromatic ring provides additional resonance stabilization through the conjugative effect.

*Carboxylic acids*

* most acidic
* presence of the carboxyl group (-COOH).
* carbonyl group is highly polarized, and the oxygen atom withdraws electron density from the adjacent carbon atom through the inductive effect, making the C-O bond more polar and weakening the O-H bond.
* The carboxylate anion is also stabilized through resonance, where the negative charge is delocalized over both oxygen atoms and the adjacent carbon atom.