Back to: Organic Chemistry 500 Level
Welcome to class!
It feels great to have you back as we continue this exciting journey through advanced organic chemistry. Today’s lesson is Spectroscopic Applications in Organic Chemistry. This is a very important area because spectroscopy is like the “eyes” of the organic chemist—it allows us to see what molecules look like, determine their structure, and confirm their identity. Without spectroscopy, it would be almost impossible to develop new drugs, agrochemicals, or materials that impact our daily lives.
Spectroscopic Applications In Organic Chemistry
Imagine you are at Balogun Market in Lagos, trying to identify the exact type of fabric you want. At first glance, many fabrics may look alike, but when you touch them or shine light on them, you notice their unique qualities—silk feels different from cotton, and Ankara has its own designs. Spectroscopy works in the same way: even though many organic compounds look alike, each has a unique “signature” that can be revealed by how it interacts with light or other energy sources.
Principle of Spectroscopy
Spectroscopy involves the interaction of electromagnetic radiation with matter. When molecules absorb or emit energy, they give measurable signals that provide information about their structure, bonding, and environment. Different spectroscopic techniques provide different types of information, and often they are used together like puzzle pieces to get the full picture.
Ultraviolet-Visible (UV-Vis) Spectroscopy
Measures absorption of UV or visible light.
Provides information about conjugated systems (alternating double and single bonds).
Example: Beta-carotene in carrots gives an orange colour because of its extended conjugation.
In drug development, UV-Vis helps track purity and concentration.
Infrared (IR) Spectroscopy
Measures vibrations of bonds in molecules.
Each functional group (C=O, O-H, N-H, C-H) has a characteristic absorption frequency.
Example: Paracetamol shows a strong band around 1650 cm⁻¹ for the C=O group and a broad band around 3200–3500 cm⁻¹ for the O-H group.
Just as you can identify a talking drum by its sound, you can identify functional groups by their IR “vibrations”.
Nuclear Magnetic Resonance (NMR) Spectroscopy
Explores how nuclei (like hydrogen or carbon) respond to a magnetic field.
¹H NMR reveals how many types of hydrogen atoms are present and their environment.
¹³C NMR provides information about the carbon skeleton.
Example: NMR helps distinguish between ethanol and dimethyl ether, which have the same molecular formula but different structures.
Mass Spectrometry (MS)
Involves bombarding molecules with electrons to break them into fragments.
The mass-to-charge ratios of the fragments are measured, revealing molecular weight and possible structure.
Example: MS can confirm the exact molecular mass of chloroquine.
Combined Use of Spectroscopy
No single method gives the full story. For example, in identifying a new natural product:
MS gives the molecular weight.
IR identifies functional groups.
NMR confirms the full structure.
This teamwork is like how a football match requires defenders, midfielders, and strikers working together to secure victory.
Applications in Real Life
Medicine: Spectroscopy confirms drug purity and structure before approval.
Agriculture: Detects pesticide residues in food.
Environment: Monitors pollutants in air and water.
Forensics: Identifies unknown substances in criminal investigations.
Summary
- Spectroscopy helps identify and study molecular structures.
- UV-Vis reveals conjugated systems.
- IR identifies functional groups through bond vibrations.
- NMR provides detailed information about hydrogen and carbon atoms in molecules.
- MS determines molecular weights and fragments.
- Combined use of spectroscopy gives complete structural information.
Evaluation
- Define spectroscopy in simple terms.
- What does UV-Vis spectroscopy reveal about a molecule?
- Which functional groups can be detected by IR spectroscopy?
- How does NMR distinguish between different hydrogen environments?
- Why is it important to use different spectroscopic methods together?
Well done! You have just learnt how spectroscopy empowers chemists to “see” molecules and confirm their structures. This knowledge is a key skill that can set you apart as a scientist. Stay confident—you are not just learning theory, you are acquiring tools used by leading researchers worldwide. Afrilearn is proud to grow with you.