Definitions YR13
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What is NMR spectroscopy?
An analytical technique that allows the structure of a molecule to be determined by analysing bond and atom environments.
What is an environment (NMR)?
The environment of an atom depends on the surrounding atoms and bonds in the molecule.
What are stereoisomers?
Molecules that have the same structural formula but a different arrangement of atoms in space (E-Z/optical)
What are optical isomers?
Non-superimposable mirror images which rotate the plane of plane-polarised light in an equal amount but opposite directions.
What is plane-polarised light?
Light which oscillates in one plane.
What is a polarimeter?
Apparatus which can be used to measure the rotation of plane-polarised light.
What is a chiral carbon?
A chiral carbon has four different groups bonded to it (chiral centre/asymmetric carbon).
What are enantiomers?
Optical isomers of the same molecule
What is a racemic mixture?
A racemic mixture (racemate) is a 50-50 mixture of the two enantiomers of an optical isomer, so doesn’t rotate the plane of plane-polarised light as the rotations cancel.
What are carbonyl compounds?
Aldehydes or ketones (at A Level). The carbonyl group is C=O.
What are hydrolysis reactions?
Reactions in which a compound is split apart in a reaction involving water.
What are condensation reactions?
Reactions which join two molecules together via the removal of a small molecule (usually water).
What are condensation polymers?
Condensation polymers are produced when monomers join together via condensation reactions. This produces the polymer and a small molecule.
What is a dynamic equilibrium?
Where the rates of forwards and backwards reactions are equal, so the relative quantities of reactants and products are unchanging.
What is a closed system?
One in which the reactants and products (or anything else) cannot enter of leave
What is Le Chatilier’s principle?
This states that if a constraint (new condition) is imposed upon a system, the system will act to counteract that constraint.
What is the equilibrium constant?
Symbol Kc or Kp, it is a ratio between the reactants and products at equilibrium. It is constant unless the temperature of the equilibrium system is changed.
What is a homogenous system?
One in which all reactants and products are in the same states.
What is a heterogenous system?
One in which not all reactants and products are in the same state.
What is the partial pressure of a gas?
The pressure it would exert if it alone filled its container. Calculated via mole fraction of gas x total pressure.
What is a Brønsted-Lowry acid?
A proton donor.
What is a Brønsted-Lowry base?
A proton acceptor.
What is a conjugate acid?
Formed when a base accepts a proton.
What is a conjugate base?
Formed when an acid donates a proton.