A sigma bond is a covalent bond formed by the end-on overlap of two atomic orbitals lying along the axis of the bond
What is a pi bond?
A pi bond is a covalent bond formed by the sideways overlap of two parallel atomic orbitals lyingperpendicular to the axis of the bond
Which are stronger, pi bonds or sigma bonds?
Sigma bonds (as the end-on overlap is much moreefficient than side-on overlap)
What is hybridisation?
The process of mixing atomic orbitals in an atom to generate a set of new atomic orbitals called hybrid orbitals
What is sp3 bonding? And what type of hydrocarbons is it found in?
sp3 bonding is when the three 2p orbitals and one 2s orbital mix to form degenerate hybrid orbitals
Alkanes
What is sp2 bonding? And what type of hydrocarbons is it found in?
sp2 bonding is when the 2s orbital and two 2p orbitals mix to form hybrid orbitals
Alkenes
Alliances undergo substitution reactions with chlorine and bromine by a _______ _________ mechanism?
chain reaction
What are the three stages in a chain reaction?
Initiation
Propagation
Termination
What happens in the initiation step if methane is reacted with Cl?
Ultraviolet light provides energy for the reaction to start. Homolytic fission of Cl or Br occurs. This creates free radicals (atoms or groups or atoms with an unpaired electron) which are highly reactive.
What happens in the propagation step?
Each chlorine radical that is produced goes on to attack a methane molecule removing a hydrogen atom from it to form HCl and a methyl radical: Cl. + CH4 ---> HCl + CH3.
The methyl radical then attacks a chlorine molecule to form chloromethane and another chlorine radical: CH3. + Cl2 ---> CH3Cl + Cl.
In each of the propagation steps one radicalsenders the reaction and another radical is generated . These steps sustain the reaction.
What happens in the termination step?
Reactions in which radicals are used up and noT regenerated eg
CH3. + Cl. ---> CH3Cl
CH3. + CH3. ---> CH3CH3
Cl. + Cl. ---> Cl2
How can alkenes be prepared in the lab?
Dehydration of alcohols
Base-induced elimination of hydrogen halides from monohalogenoalkanes
How are alcohols dehydrated in the lab?
By passing them over hot aluminium chloride or using concentrated sulphuric acid or orthophosphoric acid
Alkenes undergo addition reactions with hydrogen to form...?
Alkanes
Alkenes undergo addition reactions with halogens to form...?
Dihaloalkanes
Alkenes undergo addition reactions with hydrogen halides to form...?
Monohalogenoalkanes
Alkenes undergo addition reactions with water to form...?
Alcohols
The addition reaction of an alkene with hydrogen is also known as...? What is it catalysed by?
Hydrogenation
Nickel or platinum
The addition reaction of an alkene with a halogen is also known as...?
Halogenation
The addition reaction of an alkene with hydrogen halide is also known as...?
Hydrohalogenation
The addition reaction of an alkene with water is also known as...? What is it catalysed by?
Hydration
Acid
What is Markovnikov's rule?
Marokovinikov's rule states that when H-X or H-OH adds onto an unsymmetrical Allende the major product is the one in which the H atom ends up attached to the carbon atom of the double bond which already has the greater number of hydrogen atoms bonded to it
What type of intermediate is involved in the mechanisms in the of the following reactions:
Halogenation?
Hydrohalogenation?
Acid-catalysed hydration?
A cyclic ion intermediate
A carbocation intermediate
A carbocation intermediate
What is the difference between a primary, secondary and tertiary monohalogenoalkane?
Primary - halogen atom on carbon attached to 1 other carbon atom
Secondary - halogen atom on carbon attached to 2 carbon atoms
Tertiary - halogen atom on carbon attached to 3 carbon atoms
What is the main reaction of monohalogenoalkanes?
Nucleophilic substitution
Monohalogenoalkanes undergo elimination reactions to form...?
Alkenes
Monohalogenoalkanes react with alkalis to form...?
Alcohols
Monohalogenoalkanes react with alcoholic alkoxides to form...?
Ethers
Monohalogenoalkanes react with ethanolic cyanides to form...?
Nitriles (which can be hydrolysed to carboxylic acids)
Monohalogenoalkanes react with ammonia to form...?
Amines
Author
Anonymous
ID
211580
Card Set
Hydrocarbons and Halogenoalkanes
Description
Advanced Higher Chemistry - Unit Three - Hydrocarbons and Halogenoalkanes