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Spectroscopy and Chromatography

Integration curves

  • 3 things to know
  • Unit A2 2

Overview

Recall questions on what the integration curve shows and how the step heights are read, why area is proportional to the number of hydrogens, that only a ratio is given, assigning ethanol's 3 : 2 : 1, identifying compounds from a 6 : 1 : 1 and a 9 : 1 ratio, simplifying measured heights, and confirming an OH by shaking with deuterium oxide.

What you need to know

Answer each one before you reveal it.

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Key term

What does an integration curve show, how is it read, why does it work, and what does ethanol's 3 : 2 : 1 mean?

Key term

What does the integration curve on an nmr spectrum show?

Key term

How is an nmr integration curve read?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What does the integration curve on an nmr spectrum show?

    Model answer

    The relative number of hydrogen atoms responsible for each peak.

  2. 2

    How is the integration curve read?

    Model answer

    The vertical rise of the step above each peak is measured, and the rises are compared as a ratio.

  3. 3

    Why does the area under a peak measure the number of hydrogens?

    Model answer

    Each hydrogen nucleus in that environment absorbs equally, so the total absorption is proportional to how many of them there are.

  4. 4

    Does the integration give the actual number of hydrogens?

    Model answer

    No, it gives only their ratio, so it must be combined with the molecular formula to give actual numbers.

  5. 5

    Ethanol gives steps in the ratio 3 : 2 : 1. Assign them.

    Model answer

    Three for the CH₃ group, two for the CH₂ group and one for the OH.

  6. 6

    A compound of formula C₃H₈O shows steps in the ratio 6 : 1 : 1. What is it?

    Model answer

    Propan-2-ol, with six equivalent methyl hydrogens, one CH and one OH.

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