Introduction

Mass spectrometry provides information about molecular mass and fragmentation patterns.

Combined with infrared and NMR spectroscopy, mass spectrometry allows chemists to determine molecular structures.

The process resembles solving a puzzle in which multiple pieces of evidence must be integrated.

Molecular Mass

Mass spectrometry provides clues regarding:

• molecular weight,
• isotopic patterns,
• and fragmentation.

These features help narrow structural possibilities.

Combining Evidence

Experienced chemists rarely rely upon a single technique.

Instead, they integrate:

Infrared Spectroscopy

Functional groups.

Proton NMR

Hydrogen environments.

Carbon NMR

Carbon environments.

Mass Spectrometry

Molecular mass and fragmentation.

Together, these methods provide a remarkably powerful framework for determining molecular structure.

Structure Determination

Beginning students often view spectroscopy as a collection of unrelated techniques.

Experienced chemists treat spectroscopy as a process of assembling evidence.

The goal is not memorization but interpretation.

Themes That Reappear

Throughout spectroscopy, familiar ideas continue to appear:

• functional groups,
• symmetry,
• structure,
• pattern recognition,
• and intuition.

Organic chemistry repeatedly revisits the same principles from new perspectives.

Self-Assessment

I can:

☐ Explain what mass spectrometry reveals about a molecule.

☐ Recognize the role of fragmentation in structure determination.

☐ Combine IR, NMR, and MS evidence into a single structural proposal.

Looking Ahead

Spectroscopy reveals what molecules are.

The final part of the handbook explores how chemists decide what molecules should become.

This shift from analysis to design introduces retrosynthesis, strategy, and the art of molecular construction.

Common fragment losses and diagnostic ions are collected in Appendix D.