What happens when aqueous bromine is added to an unsaturated compound in the dark?
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It turns from reddish-brown to colourless (or decolourises).
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What happens when aqueous bromine is added to an unsaturated compound in the dark?
It turns from reddish-brown to colourless (or decolourises).
What is an addition reaction?
A reaction in which two substances combine to form a single product.
What is the process of breaking down large alkane molecules into smaller molecules called?
Cracking.
What is the molecular formula for butane?
C4H10.
What do alkenes produce when they react with steam?
Alcohol.
How can alkenes be produced in the industry?
By cracking larger alkanes.
What type of catalyst is used in the cracking process for alkenes?
Solid catalyst (aluminium oxide).
What does it indicate if aqueous bromine remains reddish-brown?
The unknown compound is an alkane.
What do isomers differ in?
Their structural formulae.
What is the physical state of Propene at room temperature and pressure?
Gas
In the compound 3-ethylpentane, what is the position of the branched chain?
At the third carbon of the pentane chain.
What are the reactants in the reaction of butene with chlorine gas?
Butene (C4H8) and chlorine gas (Cl2).
How do melting and boiling points change with an increase in the number of carbon atoms in alkenes?
They increase.
What catalyst is used in the hydration of alkenes?
Phosphoric acid (H₃PO₄).
How does viscosity change down the alkene series?
It increases.
What is the chemical equation for the reaction of bromine with an alkene?
C2H4 + Br2 → C2H4Br2.
What is required for the reaction of alkenes with halogens to occur?
Specific conditions.
How does the boiling point change in the alkene series?
The boiling point generally increases with the increasing number of carbon atoms.
What is used to distinguish between alkenes and alkanes?
Aqueous bromine.
What term describes the change in color of bromine solution when it reacts with alkenes?
Decolourises.
What process is represented by the equation C12H26 → C8H16 + C4H8 + C7H14 + H2 + C5H10?
Cracking.
What is the branched chain represented by CH3?
Methyl.
What type of hydrocarbons are produced from the cracking of dodecane?
Alkenes.
What is the second step in identifying isomerism in alkanes?
Identify the branched chain.
What catalyst is commonly used for hydrogenation of alkenes?
Nickel catalyst.
What are the two main types of isomerism?
Structural isomerism and stereoisomerism.
What happens to chain length down the alkene series?
It increases.
What is stereoisomerism?
Stereoisomerism occurs when compounds have the same molecular formula and connectivity but differ in the spatial arrangement of atoms.
How many structural isomers can butane (C4H10) have?
Butane can have two structural isomers: n-butane and isobutane.
What is the difference between cis and trans isomers?
Cis isomers have substituents on the same side of the double bond, while trans isomers have substituents on opposite sides.
What is the initial color of bromine solution before reacting with alkenes?
Reddish-brown.
What type of product is formed in an addition reaction?
A single product.
What is the example reaction of ethene with hydrogen?
C2H4 + H2 → C2H6.
What is the reaction of alkenes with steam called?
Hydration.
What is the boiling point of Butene?
-7 °C
What is isomerism?
Isomerism is the phenomenon where compounds have the same molecular formula but different structural arrangements.
What is the combustion reaction for butene (C4H8)?
C4H8 + 6O2 → 4CO2 + 4H2O.
What is the example reaction of ethene with steam?
C₂H₄ + H₂O → C₂H₅OH.
What is an example of structural isomers in alkanes?
Butane (C4H10) has two structural isomers: n-butane and isobutane.
What temperature is required for the cracking process in industrial production of alkenes?
High temperature.
What process is used industrially to produce smaller alkenes?
Cracking.
What is another example of a cracking reaction involving C3H6?
C3H6 + C9H20.
Why are smaller alkanes produced through cracking?
They are in higher demand compared to longer chain alkanes.
What can smaller alkenes be used for besides making plastics?
As fuel or starting materials for the manufacture of ammonia.
What is the branched chain represented by C2H5?
Ethyl.
What distinguishes a branched-chain alkane?
It has a carbon chain with branches.
What is the required temperature for the hydration of alkenes?
300 °C.
What is the molecular formula for 3-ethylpentane?
C7H16.
What is the combustion reaction for ethene (C2H4)?
C2H4 + 3O2 → 2CO2 + 2H2O.
Is there any reaction that occurs when bromine is added to an alkane?
No significant reaction occurs under normal conditions; alkanes are generally unreactive with bromine without the presence of UV light or heat.
What is the general molecular formula for alkenes?
C_nH_{2n}.
What happens to bromine solution when it reacts with alkenes?
The reddish-brown bromine solution turns colourless.
What types of products can result from the cracking of hydrocarbons?
Alkane and alkene.
What are smaller alkenes like propene and ethene used for?
As starting materials for making ethanol and plastics.
What do isomers differ in?
Their structural formulae.
What type of alkane is butane?
Straight-chain alkane.
What is the first step in identifying isomerism in alkanes?
Identify the longest carbon chain.
What type of alkane has a CH3 side chain?
Branched-chain alkane.
What part of the alkene molecule does the water molecule add to?
The double bond.
At what temperature is hydrogenation of alkenes typically performed?
200 °C to 300 °C.
What is structural isomerism?
Structural isomerism occurs when compounds have the same molecular formula but differ in the connectivity of their atoms.
What is the product of the reaction between butene and chlorine gas?
Dichlorobutane (C4H8Cl2).
Why does brown bromine decolourise when added to an alkene but not to an alkane?
Alkenes undergo addition reactions with bromine due to the presence of a double bond, resulting in decolourisation. Alkanes do not react with bromine under normal conditions because they only have single bonds.
What is the outcome of adding H2O to alkenes in the presence of a catalyst?
Hydration of alkenes, forming alcohols.
What type of isomerism is commonly observed in alkenes?
Geometric (cis-trans) isomerism due to the presence of a double bond.
What is the general reaction for the cracking of C12H26?
C12H26 → C5H10 + C7H16.
What is the molecular formula for butane?
C4H10.
What are isomers?
Compounds that have the same molecular formula but different structural formulae.
What is the molecular formula for butane?
C4H10.
What is the longest carbon chain in isomerism of alkanes with three carbons?
Propane.
How should the position of the carbon where the branched chain is linked be numbered?
The number must be as small as possible.
What distinguishes alkenes from alkanes?
Alkenes contain at least one carbon-carbon double bond, while alkanes only have single bonds.
Why does an alkene with 1 carbon atom not exist?
A minimum of two carbon atoms is needed to form a double bond (C=C).
What are the disadvantages of using bromine for identification?
Bromine is toxic and can be hazardous to handle, requiring careful safety precautions.
What do alkenes contain in their structure?
One carbon double bond (C=C).
What are isomers?
Compounds that have the same molecular formula but different structural formulae.
What is the molecular formula of dodecane?
C12H26.
What is the boiling point of Ethene?
-102 °C
What do alkenes produce when they combust in air?
Carbon dioxide gas and water vapor.
What are the two main types of isomerism in alkanes?
Structural isomerism and stereoisomerism.
What is the required pressure for the hydration of alkenes?
60 atm (or 6000 kPa).
What pressure is often used in the hydrogenation of alkenes?
60 atm.
How does density change down the alkene series?
It increases.
What reaction occurs when bromine is added to an alkene?
Bromine adds across the double bond of the alkene, forming a dibrominated alkane. For example: C2H4 + Br2 → C2H4Br2.
Why do we use bromine to help in identifying alkenes and not other chemicals?
Bromine is effective because it readily reacts with alkenes, causing a visible colour change, which is easy to observe.
Which halogens commonly react with alkenes?
Chlorine and bromine.
What type of compound is indicated if aqueous bromine decolourises?
An alkene.
What are the products of cracking dodecane?
Alkenes and hydrogen.
What is the characteristic of a straight-chain alkane?
Carbon atoms are joined up in a row.
What is the general reaction type involving alkenes and hydrogen?
Hydrogenation.
What is the reaction of butene with chlorine gas an example of?
Addition reaction of alkenes.
What is the combustion reaction for propene (C3H6)?
2C3H6 + 9O2 → 6CO2 + 6H2O.
What is structural isomerism?
Structural isomerism occurs when compounds have the same molecular formula but different connectivity of atoms.
What is the role of phosphoric acid in alkene reactions?
It acts as a catalyst in hydration reactions.
What are the reactants in the addition reaction involving alkenes, H2, and Br2?
Alkenes, hydrogen (H2), and bromine (Br2).
What type of isomerism is common in alkenes due to the presence of a double bond?
Geometric isomerism (cis-trans isomerism).
What are the advantages of using bromine for identification?
Bromine provides a clear and immediate visual indication of the presence of alkenes through decolourisation.
What is the branched chain represented by C3H7?
Propyl.
What is isomerism in alkanes?
Isomerism in alkanes refers to the existence of compounds with the same molecular formula but different structural arrangements.
What is the boiling point of Pentene?
30 °C
What is the chemical formula for butene?
C4H8.
What is stereoisomerism?
Stereoisomerism occurs when compounds have the same molecular formula and connectivity but differ in the spatial arrangement of atoms.
Can alkanes exhibit geometric isomerism?
No, alkanes do not exhibit geometric isomerism due to the lack of double bonds.
What type of hydrocarbons are alkenes classified as?
A homologous series.
What is the general formula for alkenes?
CnH2n, where n is the number of carbon atoms.
What is the molecular formula for ethene?
C2H4.
What is the first member of the alkene homologous series?
Ethene (C2H4).
What is the general formula for alkenes?
Each alkene contains C=C.
By how many units does each member of the alkene series differ from the next?
By a CH2 unit.
How is hydrogen added to ethene during hydrogenation?
At the C=C bond of ethene (unsaturated).
What is the chemical formula for propene?
C3H6.
What is the product of the reaction of propene with hydrogen gas?
Propane (C3H8).
What is the general outcome of hydrogenation of alkenes?
Conversion of alkenes to alkanes.
What do alkenes produce when they react with halogens?
Halogenoalkanes.
What is the structural formula for propene?
C3H6.
What type of bond is broken in the reaction of alkenes with halogens?
The double bond (C=C).
What is the molecular formula for butene?
C4H8.
What is the example reaction of ethene with bromine?
C2H4 + Br2 → C2H4Br2.
What is the molecular formula for pentene?
C5H10.
What suffix do the names of alkenes end with?
-ene.
What type of hydrocarbons are alkenes?
Unsaturated hydrocarbons.
What do alkenes produce when they react with hydrogen?
Alkanes.
What is the reaction called when alkenes react with hydrogen?
Hydrogenation.
What conditions are required for the hydrogenation of alkenes?
Nickel catalyst and a temperature of 200 °C.
What is a homologous series?
A group of organic compounds with the same functional group and similar chemical properties, differing by a constant unit.
What type of reaction occurs when propene reacts with hydrogen gas?
Hydrogenation.
