Chromatography + NMR Flashcards
Explain why carbon 13 is used for NMR instead of C12.
→ C-13 has an odd number of nucleons
→ therefore they have a nuclear spin
State why TMS is used as a standard.
→ inert
→ volatile
→ non-toxic
What is the chemical shift?
the difference between the TMS peak and the peaks produced by sample
Which elements have a higher chemical shift and why?
- ones that are next to electronegative atoms
- less electron shielding so more affected by magnetic field
State what the integration values tells us in H1 NMR.
the number of hydrogen atoms in each environment
Explain the splitting pattern and the n+1 rule.
no. of peaks for an atom is 1 plus the number of hydrogen atoms on adjacent atom:
singlet → zero H atoms on neighbouring atom
doublet → 1 H atom on neighbouring atom
triplet → 2 H atoms on neighbouring atom
State and explain which type of solvent is used for H1 NMR
- non hydrogen based solvents e.g CCl4, deuterium
- have no H atoms so will not give any peaks in the spectrum
State the stationery phase used in TLC.
→ silica/alumina mounted on a glass plate
State two ways in which colourless compounds can be seen in TLC.
→ iodine
→ UV light
Briefly explain how column chromatography works.
→ glass tube filled with silica (stationery phase)
→ mixture/solvent is run through the column
→ each component reaches the end of column at different times
State the stationery phase used in gas chromatography.
viscous liquid with high boiling point
(lined onto the column)
State the mobile phase used in gas chromatography.
inert gas
