Course

A2 Chemistry: Analysis and Spectroscopy (9701)

Name: A2 Chemistry: Analysis and Spectroscopy (9701)
Price: 1499 BDT

Mass gives the size, infrared gives the groups, NMR gives the arrangement. Separate the mixture first, then take one spectrum apart four different ways.

13 lessons1h 14mEnglish

What you'll learn

Explain separation as a competition between a stationary and a mobile phase
Calculate a retention factor and explain why a ratio is quoted rather than a distance
Interpret a gas-liquid chromatogram, using retention time for identity and peak area for amount
Explain why chromatography is joined to mass spectrometry, and count carbons from an M+1 peak
Explain the origin of an NMR signal and why shielding decides the chemical shift
Count proton environments in a molecule, including where symmetry reduces them
Read an integration trace as a ratio and convert it to protons using the molecular formula
Apply the n + 1 rule, counting neighbours on every adjacent carbon
Explain why the lines of a multiplet differ in height and why a septet is often misread
Explain the D2O experiment and why an exchangeable proton neither splits nor is split
Use a carbon-13 spectrum to count carbon environments
Combine mass, infrared and NMR evidence to identify an unknown, quoting absences as evidence
Distinguish two isomers of the same molecular formula from their proton NMR spectra

Requirements

AS analytical techniques: reading a mass spectrum and an infrared trace
AS organic chemistry: functional groups, homologous series and structural isomerism
AS stoichiometry: relative molecular mass from a molecular formula

Course content

13 lessons · 1h 14m

37.1-37.2 · Chromatography

One competition between a stationary and a mobile phase, measured as a distance ratio on a plate and as a time in a column. Ends by joining the column to a mass spectrometer.

0/3

Separating before identifying

Two phases and a competition between them, measured as Rf: a ratio, so it does not depend on how long the plate ran.

Preview7m 2.

Gas-liquid chromatography

The same idea in a column. Retention time says what is present and peak area says how much.

Preview7m

Joining the two machines

Chromatography separates and does not identify; mass spectrometry identifies and cannot cope with a mixture. GC-MS, and counting carbons from M+1.

37.3-37.4 · Nuclear magnetic resonance

Four readings of one spectrum: how many signals, where, how tall, how many lines. Then the drop of D₂O that proves an O-H, and the carbon-13 spectrum that counts carbons.

0/4

What NMR measures

A proton flips in a magnetic field, and the electrons around it decide how much field it feels. That shielding is the chemical shift.

Preview7m 2.

Environments and integration

One signal per environment, and a staircase that gives the RATIO of protons rather than their number.

Preview7m

Splitting and the n + 1 rule

Count the lines and you have counted the neighbours. The heights follow Pascal, which is why a septet gets misread.

D₂O and carbon-13

A peak that disappears proves an O-H, because the proton has left the molecule. Carbon-13 then counts carbon environments.

Identifying an unknown

Mass gives the size, infrared gives the groups, NMR gives the arrangement. Then two isomers that share a formula, where only the spectrum can decide.

0/3

Combining the evidence

What each technique is for, in the order to use them, and why the absence of a band is evidence worth writing down.

Preview8m 2.

Two isomers, one formula

When the mass spectrum and the infrared both tie, the proton NMR decides. The septet rules out propan-1-ol on its own.

Preview8m

Analysis: exam question

One structured Paper 4 question that runs an unknown through chromatography, mass spectrometry, infrared and NMR.

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