AQA Paper 2 Past Paper Errors Flashcards
Draw struture of the zwitterion formed by phenylalanine
Phenyl must replace hydrogen in CH3 not CH due to stability and hydrogen in CH3 is more reactive
Draw struture of serine at high pH
IUPAC name of this compound
N-ethylpropanamide
State in general terms what determines the distance travelled by a spot in TLC.
solubility in moving phase and relevant affinity for stationary phase
To obtain the chromatogram, the TLC plate was held by the edges and placed in the solvent in the beaker in the fume cupboard. The lid was then replaced on the beaker.
Give one other practical requirement when placing the plate in the beaker
solvent depth must be below start line
Deduce the relative polarities of the 1,2-dinitrobenzene and 1,4-dinitrobenzene and explain why 1,4-dinitrobenzene has the greater Rf value.
The Rf value of 1,4-dinitrobenzene is greater than that of 1,2-dinitrobenzene because 1,4-dinitrobenzene is less polar.
The greater polarity of 1,2-dinitrobenzene means it interacts more strongly with the stationary phase in the TLC experiment, so it travels less and has a lower Rf value.
(dont need to put this next part but it just explains why 1,2- is more polar) 1,2-Dinitrobenzene has two nitro groups positioned close together (ortho position), which results in stronger dipole-dipole interactions, making it more polar.
A TLC experiment was carried out and the solvent contained hexane and the rf value of 1,2-dinitrobenzene was measured. In a new experiment the solvent contained a mixture of hexane and ethyl ethanoate. Is the rf value of 1.2-dinitrobenzene in the second experiment larger than the rf value in the first experiment
Yes
ethyl ethanoate is not symmetrical hence it is polar, hence the solvent is more polar
Polar isomer more soluble / has stronger affinity than the solvent before
