Organic Chemistry

Catalysis is a major part of modern technology. It helps chemical reactions happen by lowering activation energy, which is the energy needed to start a reaction. Catalysts can also affect selectivity, or which products form during a reaction.

Catalysis has a large impact on industry and daily life. It is linked to about 35% of global GDP. It also supports the food supply for about 33% of the world’s population through fertilizers made by the Haber process.

Because catalysts improve how...

A reflux setup lets chemists heat reactants without losing material to evaporation. Many chemical experiments need elevated temperatures before a reaction starts. When the reactants or solvent have low boiling points, heating can cause them to escape as vapor.

A reflux system prevents that loss by condensing the vapor that forms during heating. The condensed liquid then flows back into the reaction vessel. This keeps the reactants and solvent in the flask while the reaction is heated.

Low-temperature reactions are often run with cooling baths to keep the reaction flask below room temperature. Chemists use this setup when they want a reaction to stay within a specific temperature range. The reagents in the flask do not touch the cooling bath itself.

Reaction rate depends on molecular collisions. At higher temperatures, atoms and molecules move faster, collide more often, and react more effectively. A common rule of thumb based on the Arrhenius equation says that raising the...

Schlenk lines and high vacuum lines are used to move solvents without exposing them to moisture or oxygen. They do this by keeping reactions under a slight overpressure of inert gas, usually nitrogen or argon, or by using vacuum.

Vacuum transfer is a separate method for isolating solvents and other volatile reagents from drying agents or other nonvolatile materials. It lets users dispense clean solvent into a reaction vessel or storage vessel while the air-free environment is maintained. The...

Freeze-pump-thaw cycling is a method for removing dissolved gases from a liquid. Degassing means taking dissolved gases out of a liquid. These gases can include oxygen or carbon dioxide.

Dissolved gases can cause problems in the lab. They can interfere with chemical reactions that use sensitive reagents. They can also affect spectroscopic measurements and cause unwanted bubble formation.

Several methods can be used to degas liquids. These include heating, ultrasonic agitation, chemical...

Many organic reactions must be set up without water. Moisture in the air can react with sensitive reagents before the reaction even starts. When that happens, the desired reaction may fail or give poor yields because the reactants have changed chemically.

To prevent this, the reaction is run under an inert atmosphere. An inert atmosphere is a gas environment that does not react easily with the chemicals in the flask. Nitrogen gas is often used, and argon may be used for reactions that are even...

Recrystallization is a technique for purifying solid compounds. It uses the fact that solids are often more soluble in hot liquids than in cold liquids. An impure solid is dissolved in a hot liquid until the solution becomes saturated, meaning it holds as much dissolved material as it can at that temperature.

The solution is then allowed to cool. As the temperature drops, the compound should form relatively pure crystals. Most impurities should stay in the solution and not become part of the...

Solubility-based separation removes a compound from a mixture by making it insoluble in water. Most samples of interest contain many different components, so sample preparation is an important step before analysis. It helps remove interferences that could affect the results. This separation method is useful in both academic and industrial settings.

The process relies on the solubility properties of compounds in aqueous solutions. A compound’s solubility can depend on ionic strength, pH, and...

Solid samples can be prepared for chemical analysis by moving the target analyte into a liquid. This solid-liquid extraction step is used in many chemical analyses before spectroscopic or chromatographic identification and quantification. It helps separate the analyte from the rest of the sample matrix, which is the material surrounding it.

A simple approach is to mix the solid with a solvent that can dissolve the analyte. Agitation helps the analyte leave the solid and partition into the...

Rotary evaporation is a common lab method for drying and purifying samples in organic chemistry. It helps remove a solvent from a compound of interest when the compound has a higher boiling point. A rotary evaporator is often called a rotovap.

The rotovap was invented in 1950 by the chemist Lyman C. Craig. It is widely used because it works quickly and can handle large volumes of solvent. For this reason, many laboratories prefer rotary evaporation when they need to remove low boiling point...

Fractional distillation separates liquid mixtures by using differences in boiling point. Chemists use this lab technique to purify organic liquids. When a mixture is carefully distilled, compounds with different boiling points split into individual parts.

There are two main types of distillation: simple distillation and fractional distillation. Simple distillation is used when a liquid is relatively pure, when it contains no more than 10% liquid contaminants, or when it has a non-volatile...

X-ray crystal growth is a key step in X-ray crystallography, the method used to determine the spatial arrangement of atoms in a crystalline solid. That structure reveals the three-dimensional shape of a molecule or complex. Since structure and function are closely linked, this information can help explain a compound's behavior and reactivity.

X-ray crystallography is one of the most useful ways to solve a compound's three-dimensional structure. In some cases, it may be the only practical...

Thin layer chromatography separates mixtures of non-volatile compounds. It uses a TLC plate with a thin layer of adsorbent material as the stationary phase. The adsorbent layer is fixed to a solid support such as plastic, aluminum, or glass.

The sample and a reference compound are first dissolved in a suitable solvent. They are then applied as small spots near the bottom edge of the TLC plate. This placement helps the compounds move with the developing solvent in a controlled way.

To run the...

Column chromatography is a useful method for purifying compounds. It uses a stationary phase packed into a column and a mobile phase that flows through it. The separation works because different molecules have different polarities, so they move through the column at different rates.

The most common stationary phases are silica gel, or SiO2, and alumina, or Al2O3. The mobile phase is usually an organic solvent. The solvent choice depends on the polarity of the molecules being purified.

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Nuclear magnetic resonance (NMR) spectroscopy helps organic chemists study molecules and check reaction results. It can show molecular structure, sample content, and sample purity. Because NMR is non-destructive, it is useful when the sample needs to be recovered after analysis.

One of the most common methods is proton, or 1H, NMR. Protons in a molecule respond differently depending on their chemical environment. That difference makes it possible to infer the structure of the molecule from the...