Biochemistry reactions Flashcards
Describe the three steps of radical substitution.
- Initiation
-The production of free radicals. - Propagation
-The steps which produce products and more
free radicals. - Termination
-Two free radicals meet to form a product.
Describe the difference between homolytic and heterolytic fission.
Homolytic fission involves the breaking of a covalent bond where both atoms leave with one electron from the shared pair.
Heterolytic fission is where one atom takes both electrons because it is more electronegative.
What mechanism is involved in halogenation of alkenes?
Electrophilic addition
Describe two sets of conditions needed for cracking.
- High temperate and high pressure
2. Lower temperature and ZEOLITE catalysts
Describe the reactants, products, and the necessary catalyst for hydration of an alkene.
Addition of water to an alkene, forming an alcohol. Catalyst of sulphuric acid / phosphoric acid.
Describe the necessary conditions, reactants and products formed for hydrogentation of alkenes.
Addition of hydrogen.
Catalyst such as nickel or platinum.
Product is corresponding alkane.
Conditions - around 4 atm at 150-250 degrees celcius.
What reactant is used in the oxidation of alkenes to diols?
Cold dilute, acidified solution of potassium permanganate.
What reactant is used for the further oxidation of diols to carboxylic acids or ketones?
Hot concentrated, acidified solution of potassium permanganate.
In the oxidation of diols with hot concentrated acidic potassium permangante, a single carbon fragment will yield what oxidised product?
Carbon dioxide.
In the oxidation of diols with hot concentrated acidic potassium permangante, a primary alcohol fragment will yield what oxidised product?
Carboxylic acid.
In the oxidation of diols with hot concentrated acidic potassium permangante, a secondary alcohol fragment will yield what oxidised product?
Ketone.
What is the mechanism involved in addition polymerisation?
Free radical.
Describe two methods of producing methanol.
- Hydrogenation of carbon monoxide with synthesis gas (200-300 degrees, 100 atm H2 gas) over a copper catalyst.
- Dry distillation of wood.
Describe a method of producing ethanol.
Fermentation of sugar using yeast enzyme.
How can any alcohol be formed?
From the hydration of alkenes using a catalyst of concentrated phosphoric acid.
What are the products of combustion of alcohols?
Water and carbon dioxide.
What are the two most common oxidising agents for alcohols?
Acidified potassium dichromate and acidified potassium permanganate.
What are some steps necessary to obtain a desired product of aldehyde when oxidising a primary alcohol, and how is it possible?
Use a mild oxidising agent (acidified potassium dichromate) / limited oxidising agent / excess alcohol and DISTILLATION. Aldehydes have low boiling points because of no hydrogen bonding.
What will be the product of oxidising a secondary alcohol?
Ketone.
What will be the product of oxidising a tertiary alcohol.
No product. Tertiary alcohols cannot be oxidised.
What are the colour changes for two reagents which show a positive test for the oxidisation of a primary or secondary alcohol?
Acidified potassium dichromate - orange to green
Acidified potassium permanganate - purple to colourless
What must be present in an alcohol»_space; haloalkane substitution reaction for it to take place?
A strong acid.
What is the product formed and catalyst required for a dehydration of an alcohol.
Alkene. Acid catalyst.
Describe the steps to obtain an ester from an alcohol and a carboxylic acid. Name this reaction.
Esterification of alcohol with carboxylic acid. Requires concentrated sulfuric acid catalyst and reflux (because it is an equilibrium reaction).
