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MASS SPECTROMETRY (MS)

MASS SPECTROMETRY (MS). Mass Spectrometry . MS gives an exact measure of molecular mass. An electron beam (70ev) dislodges an electron from a sample giving M + , a radical cation . A potential difference of ~10000 v accelerates the ions. Radicals are not affected.

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MASS SPECTROMETRY (MS)

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  1. MASSSPECTROMETRY(MS)

  2. Mass Spectrometry MS gives an exact measure of molecular mass. An electron beam (70ev) dislodges an electron from a sample giving M+ , a radical cation. A potential difference of ~10000 v accelerates the ions. Radicals are not affected. The ions pass through a magnetic field causing the ions to curve (heavier ones less than lighter ones). Radicals are not affected by the magnetic field. Ions collide with the detector to give a spectrum with particles arranged by mass. •

  3. Mass Spectrometry The most intense peak is called the base peak. The highest MW peak is the usually the molecular ion, M+ or M, and equals the MW of the compound. Isotopes of certain atoms produce M+1 and M+2 peaks, some of which are very characteristic. Odd numbers of nitrogen give an odd M peak. The radical cation is unstable and fragments during flight. Fragment weights can assist in determining structure. M+ A+ + B or A + B+ • • •

  4. Isotopic Abundances

  5. Mass Spectrometry – Linear Alkane CH3CH2CH2CH2CH2CH3

  6. Mass Spectrometry – Branched Alkane

  7. Mass Spectrometry – Branched Alkane

  8. Mass Spectrometry - Alkene

  9. Mass Spectrometry - Chloroalkane

  10. Mass Spectrometry - Bromoalkane

  11. Mass Spectrometry – Sulfide

  12. Mass Spectrometry - Alcohol

  13. ENDMASSSPECTROMETRY(MS)

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