Organic Practicals Flashcards
Compare the rates of hydrolysis of 1- chlorobutane ,1-bromobutane and 1-iodobutane what would appear first
Silver iodide then silver bromide formed and then silver chloride formed
Due to bond strength C-I is weaker then an C-Br and and then C-cl is weaker
What is reagent used for hydrolysis of halogenoalkanes
Aqueous silver nitrate
The leaving group combines with silver nitrate
What is the precipitate formed for the halogen hydrolysis reactions
Silver halide precipitate
Give additional reagent to form carboxylic acid
Dilute sulfuric acid
What is the role of anti bumping granules
To prevent large bubbles
How do you test the difference between carboxylic acid and alcohol
Add sodium carbonate
Effervescence bubbles produced
When substance is heated in reflux ,how must the condenser appear
Never sealed
Condenser must have two openings for water in and out
Why is sodium carbonate added when forming an ester and why there is build up in pressure
To neutralise
CO2 is produced
How are esters hydrolysed
Under reflux
Using dilute HCL
Describe the formation of ester practical
Propane acid and ethanol mixed to round bottom flask
Concentrated sulfuric acid added
When acid has been added, reflux condenser is fitted to the flask and heated with electric heating mantle
The mixture is cooled and rearranged for distillation
Distillate placed in separating funnel and shaken
Ester is run into dry flask containing anhydrous calcium chloride
Filters with anti bumping granules
Why is electric heater used for formation of ester
Controls heating because it can be extremely flammable
Why is calcium chloride used in formation of ester
It is a drying agent
describe the distillation of primary alcohol
Place dilute sulfuric acid in a flask and add potassium dichromate(VI) and 2 or 3 anti- bumping granules.
-Shake the contents of the flask until solution is complete (do not warm).
- Add propan-1-ol in drops from a dropping pipette, shaking the flask so as to mix the contents, and then assemble distillation apparatus as shown below
- Gently heat and slowly distil liquid into a test tube, taking care that none of the reaction mixture splashes over.
what is the group test for alkene and result
bromine water in a test tube add a few drops of the unknown and shake.
Observation: alkenes should decolourise bromine water
how is tollens reagent formed
Reagent: Tollens’ reagent formed by mixing aqueous ammonia and silver
nitrate. The active substance is the complex ion of [Ag(NH3)2]+
what is the test for aldehyde using tollens reagent
Conditions: heat gently
Reaction: aldehydes only are oxidised by Tollens’ reagent into a carboxylic acid. The silver(I) ions are reduced to silver atoms
Observation: with aldehydes, a silver mirror forms coating the inside of the
test tube. Ketones result in no change.
describe the test for aldehydes using fehlings
Reagent: Fehling’s solution containing blue Cu 2+ ions.
Conditions: heat gently
Reaction: aldehydes only are oxidised by Fehling’s Solution
into a carboxylic acid. The copper (II) ions are reduced
to copper(I) oxide .
Observation: Aldehydes: Blue Cu 2+ ions in solution change
to a red precipitate of Cu2O. Ketones do not react
how do you test for the presence of carboxylic acid
The presence of a carboxylic acid can be tested by
addition of sodium carbonate. It will fizz and produce
carbon dioxide.
what reagent is used in the test for alcohol
potassium dichromate and sulfuric acid
what is the test of chloroalkane
warm with silver nitrate
formation of white precipitate of AgCl
what is aspirin made of
Aspirin is made from 2-hydroxybenzoic acid which contains a phenol group.
In the reaction the phenol group is turned into an
ester by reacting it with the reactive ethanoic anhydride
what type of reaction is the formation of aspirin
esterification
how are insoluble impurities removed
Hot filter solution through (fluted) filter paper quickly.
how do you test for the degree of accuracy
One way of testing for the degree of purity is to determine the melting
“point”,
how is the melting point lowered
If impurities are present (and this can include solvent from the
recrystallisation process) the melting point will be lowered and the
sample will melt over a range of several degrees Celsius
how is melting point measured
Melting point can be measured in an electronic melting point machine
describe the practical for thin layer chromatography
1.draw a pencil line 1 cm above the bottom of a
TLC plate and mark spots for each sample, equally spaced along line.
2) Use a capillary tube to add a tiny drop of each solution to a
different spot and allow the plate to air dry.
3) Add solvent to a chamber or large beaker with a lid
4) Place the TLC plate into the chamber, making sure that the level of the solvent is below the pencil line. Replace the lid to get a tight seal.
5) When the level of the solvent reaches about 1 cm from the top
of the plate, remove the plate and mark the solvent level with a
pencil. Allow the plate to dry in the fume cupboard.
f) Place the plate under a UV lamp in order to see the spots. Draw around them lightly in pencil.
g) Calculate the Rf values of the observed spots.
why do we draw a pencil line
pencil line –will not dissolve in the solvent
why do we use a tiny spot on the line
too big a drop will cause different
spots to merge
why is a lid used
lid– to prevent evaporation of toxic solvent
why is dryed in a fume cupboard
dry in a fume cupboard as the solvent is toxic
what is the rf value
Rf value = distance moved by amino acid divided by
distance moved by the solvent
what does the seperation of chromatography depend on
Separation by chromatography depends on the balance between solubility in the moving phase and retention in the stationary phase.
For oxidation of secondary alcohol how is the apparatus meant to be set up
Needs to have anti bumping granules
To create smaller bubbles
System should be closed
Stops gases from escaping since it’s volatile
Water should be flowing the right direction
Water should be going in at the furthest end of the condenser
What technique is used to separate propane acid from reaction mixture
Fractional distillation
In the formation of cyclohexene why is sodium chloride added
Help separate the organic layer from the aqueous layer
In the formation of cyclohexane why is anhydrous calcium chloride added
It is insoluble in cyclohexene
Acts as a drying agent
