Synthesis Flashcards
What is bond fission?
The process of bond breaking is known as bond fission.
What is homolytic bond fission?
-results in the formation of two neutral radicals
-occurs when each atom retains one electron from the sigma covalent bond and the bond breaks evenly
- normally occurs when non-polar covalent bonds are broken
What is heterolytic bond fission?
-results in the formation of two oppositely charged ions
- occurs when one atom retains both electrons from the sigma covalent bond and the bond breaks unevenly
-normally occurs when polar covalent bonds are broken
What are nucleophiles?
negatively charged ions or neutral molecules that are electron
rich, such as
Cl^- , Br^- , OH^- , CN^-
, NH3 and H2O
What are nucleophiles attracted to?
attracted towards atoms bearing a partial or full positive charge
What are electrophiles?
positively charged ions or neutral molecules that are electron
deficient, such as
H^+, NO2^+ and SO3
What are electrophiles attracted to?
attracted towards atoms bearing a partial or full negative charge
What is an SN1 reaction?
SN1 is a nucleophilic substitution reaction with one species in the rate
determining step and occurs in a minimum of two steps via a trigonal
planar carbocation intermediate
What is an SN2 reaction?
SN2 is a nucleophilic substitution reaction with two species in the rate
determining step and occurs in a single step via a single five-centred,
trigonal bipyramidal transition state
What molecules favours SN1 reactions?
Tertiary molecules
What molecules favours SN2 reactions?
Primary molecules.
Why do ethers have lower boiling points than alcohols?
Due to the lack of hydrogen bonding between ether molecules, they
have lower boiling points than the corresponding isomeric alcohols
Why are larger ethers insoluble in water?
Larger ethers are insoluble in water due to their increased molecular size.
Why are ethers often used as solvents?
Ethers are commonly used as solvents since they are relatively inert chemically and will dissolve many organic compounds.
What does Markovnikov’s rule state?
Markovnikov’s rule states that when a hydrogen halide or water is added to an unsymmetrical alkene, the hydrogen atom becomes
attached to the carbon with the most hydrogen atoms attached to it
already.
Why do primary and secondary amines have higher boiling points?
display
hydrogen bonding. As a result, primary and secondary amines have
higher boiling points than isomeric tertiary amines.
Why are amines soluble in water?
hydrogen-bond
with water molecules, thus explaining the appreciable solubility of the
shorter chain length amines in water.
What has sp3 hybridisation
C-C single bonds
What has sp2 hydridisation?
C-C double bonds
What has sp hybridisation?
C-C triple bonds
What do monohaloalkanes react with to form Alcohols?
Aqueous alkali such as KOH or NaOH
What type of reaction is monohaloalkanes to alcohols?
nucleophilic substitution
What is inductive effect?
The alkyl R group have a positive inductive effect. They are electron donating and push electrons towards the positive charge on the varbon which helps to stabilise it.
What is steric effect?
The size of the alkyl group on the haloalkane causes and important effect. In SN2 mechanism the nucleophile attacks from the opposite side of the halogen. Tertiary haloalkanes with resist the attack as it is sterically hindered and the three bulky alkyl groups prevent access to the positive carbon
What do monohaloalkane react with to form ethers?
Alcoholic alkoxides
What type of reaction is monohaloalkane to ether?
nucleophilic substitution
What do monohaloalkane react with to form nitriles?
Sodium or potassium cyanide in methanol
What type of reacton is monohaloalkeane to nitriles?
Nucleophilic subsitution
What nitriles undergo to form carboxylic acids?
Acid hydrolysis 2H2O/H^+
What do monohaloalkane react with to form alkanes?
Ethanolic potassium hydroxide
What type of reaction is monohaloalkane to alkenes?
Elimination (base-induced)
What do alkenes react with to form alcohols?
Aluminium oxide, conc sulfuric acid or conc phosphoric acid
What type of reaction is alkenes to alcohols?
Dehydration
What type of reactions can alkenes undergo?
addition
What can alkenes react with to form alkanes?
Hydrogen
What can alkenes react with to form dihaloalkanes?
Halogens
What can alkenes react with to form monohaloalkanes?
Hydrogen halides
What can alkenes react with to form alcohols?
Water
What does the OH group in alcohols allow to form?
Hydrogen bonding
Why are smaller alcohols miscible in water?
Due to the hydrogen bonding with the water molecules.
Why are larger alcohols insoluble in water?
The long non-polar chain masks the polar hydroxyl group
How are alcohols formed from monohaloalkanes?
Heating monohaloalkanes under reflux with aqueous sodium or potassium hydroxide
How are alcohols formed from alkenes?
Reacting alkenes with water in the presence of an acid catalyst
How are alcohols formed from aldehydes or ketones?
Reduction of aldehydes and ketones using lithium aluminium hydride dissolved in ether
What do alcohols react with to form alkoxides?
with reactive metals such as sodium or potassum
What type of reaction is alcohols to alkoxides?
Displacement/redox
What do alcohols react with to form alkenes
aluminium oxide, con sulfuric acid or conc phosphoric acid
What type of reaction is alcohols to alkenes?
Dehydration/elimination
What do alcohols react with to form esters?
Carboxylic acids or acid chlorides
What type of reaction is alcohols to esters?
Esterification or condensation
What do aldehydes/ primary alcohols react with to form carboxylic acids?
Acidified potassium dichromate,
What do amides/esters/nitriles react with to form carboxylic acids
Hydrolyse by heating under reflux in the presence of an aqueous acid catalyst
What do carboxylic acids react with to form salts?
metals, carbonates and alkalis
What do carboxylic acids react with to form esters?
alcohols
What do carboxylic acids react with to form amides?
They react with amines to form alkylammonium salts which are then heated to form amides
What can carboxylic acids react with to form primary alcohols?
Lithium aluminium hydride
What do primary and secondary amines that can form bonds?
Have polar N-H bond so will have hydrogen bonding
Why do tertiary amines have lower boiling points than primary and secondary amines?
They do not have hydrogen bonding
Why are amines with lower molecular mass soluble in water?
They can form hydrogen bonds with water molecules
What are amines?
Weak bases and only partially dissociate in aqueous solution
What is benzene?
-C6H6
-Planar
-sp2 hybridised
What reactions will benzene undergo?
Electrophilic substitution
What is required for alkylation of benzene to occur?
Aluminium chloride
What is required for halogenation of benzene to occur?
Cl-Cl
What is required for nitration of benzene to occur?
NO2 conc nitric acids and sulfuric acids
What is required for sulfonation to occur?
HSO3 conc sulfuric acids
