Organic (2)
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Functional group of nitriles
CN
Give the functional groups of 2 derivates of Carboxylic acids
• esters: COO • Acyl Chlorides - COOCl
Functional group of amides
• NH2
define structural isomer
• same molecular formula, diff structural formula.
position isomer
same molecular formula, but diff position of functional groups
Functional group isomers, give an example.
same molecular formula, but arrange to give diff functional groups. eg alcohol to ether.
where is the COO in aldehydes?
end
where is the COO in ketones?
middle.
stereoisomerism
• same structural formula, diff arrangement of atoms in space.
Optical isomerism components (what is needed for it to happen?)
• 4 diff groups need to be attached to a carbon (an asymmetric carbon) • four groups arranged tetrahedrally around the C.
enantiomers
• 2 compounds that are optical isomers of each other. • are nonsuperimposable.
give some properties of optical isomers
• can rotate plane polarised light • similar chemical and physical properties.
define a racemic mixture
• a mixture containing 50/50 of enantiomers.
Give 1 property of a racemic mixture
• will not rotate plane polarised light. • because one will rotate clockwise, and one anticlockwise, so will cancel out.
why is trying to separate a racemic mixture extremely difficult?
• very expensive • same chemical and physical properties.
how do you form a racemate? (mechanism wise)
• forms when a trigonal planar reactant or intermediate is approached by 2 species attacking from either side.
Which type of mechanism can actually form a racemate?
• Sn1 only (happens in 2 steps)
Describe the Sn1 mechanism to form a racemate.
• any species attached to Carbon breaks off, forming a carbocation intermediate. • this is planar • 2 species can now either attack from the top or bottom, resulting in diff enantiomers forming. • can tell when it is a racemate, as will no longer rotate plane-polarised light.
Describe the Sn2 mechanism
• species attacks the carbon (slightly positive) and then jumps off to another delta negative species, breaking it off • forms a transition stage. • cannot form racemic mixture, only forms one enantiomer. (so will still rotate plane polarised light)
what two types of reactions can form a racemate?
• nucleophilic addition, and electrophilic addition.
describe and explain the trend in solubility of carbonyls in water
• smaller the carbonyl, the more soluble in water it is. • because it can form H bonds with water. • pure carbonyls cannot form hydrogen bonds, but can bond by forming permanent dipole-dipoles.
describe the reaction, reagent and conditions and observations of the oxidation of aldehydes
Reaction: aldehyde—> carboxylic acid Reagent: acidified K2Cr2O7 (with H2SO4) conditions: heat under reflux. observations: orange to green, as the Cr2O72- ion is reduced to the Cr3+ ion.
Give the conditions and test for aldehydes
• tollens reagent, heat gently (eg with water bath) • will form a silver mirror.
Give another test and conditions for aldehydes
• Fehling’s solution, heat gently (eg with water bath) • blue to brick red.