Whats in a medicine? Flashcards
(12 cards)
Heat and distil:
Heat and distil: removes the aldehyde as it forms, so no further
oxidation takes place
Heat under reflux:
the aldehyde is not removed, it condenses in the
vertical condenser and returns to the flask, so continues being oxidised
to a carboxylic acid.
explain esterification:
- Alcohol +
carboxylic acid - Warm with
catalyst
(concentrated
sulfuric acid or
concentrated
hydrochloric acid) - Add Na2CO3 after
to neutralise the
catalyst - Alcohols also
esterify with acid
anhydrides - 1o, 2o, and 3o
oxidisation:
oxidising agent is
acidified
dichromate
solution
* Colour change:
orange → green
* 1o and 2o only
dehydration:
- by heating
with Al2O3 - or refluxing
with
concentrated
sulfuric acid - 1o, 2o, and 3o
reflux technique:
Used to heat a volatile substance for a long time with no loss of products or reactants.
Vapours condense in the vertical condenser and return to the flask.
Anti-bumping granules prevent vigorous boiling
techniques and
procedures for preparing
and purifying a liquid
organic product
- Add impure liquid to a separating funnel
- Add either a carbonate solution (to neutralise
acidic impurities) or a dilute acid (to neutralise
alkaline impurities). Shake, and open occasionally to release any gas formed - Allow to separate into layers (an aqueous layer
and organic layer). Denser layer will be at the bottom - Open the tap run off the lower aqueous layer and discard.
- Run the organic layer into a conical flask.
- Add anhydrous calcium chloride to dry the
liquid. - Distil to separate the organic liquid
Purification by distillation
- Used to purify a mixture of liquids with different boiling points
- Thermometer is used to record the temperature at which the distillate is being collected
techniques and procedures
for purifying a solid organic
product (recrystallisation)
- Select solvent in which the solid is very soluble when hot but only sparingly soluble when cold
- Dissolve solid in minimum volume of hot solvent
- Filter quickly to remove insoluble impurities. Filter under reduced pressure so the process occurs quickly, before the solvent starts to cool
- Cool in ice bath to form crystals
- Filter to separate crystals from soluble impurities
- Wash crystals with small volume of ice-cold solvent
- Dry in oven (below melting point of solid) to constant mass
Melting point determination:
- The purity of a solid can be determined from its melting point.
- Impurities will lower the melting point and the solid will melt over a larger range of
temperatures
Method:
* Put crystals of the substance to be tested in a melting point tube (capillary tube sealed at
one end)
* Tap the tube to get the crystals to the bottom
* Heat slowly
- Record the temp when it starts to melt AND when it finishes melting
- If substance is pure melting range will be less than 0.5oC
- If impurities are present range is wider and lower than the true melting point
Thin layer chromatography /paper
chromatography
- Separates substances by their affinity for the mobile phase or stationary phase.
- Mobile phase: solvent
- Stationary phase: TLC plate or paper
- Used to test for purity – a pure substance will only have one spot on the chromatogram.
the principles of green
chemistry in industrial
processes:
lower temps by using catalyst or enzyme,
higher atom economy,
reduce use of organic solvents, especially chlorinated solvents,
use fewer steps
