There are two ways to determine the amount of heat involved in a chemical change: measure it experimentally, or calculate it from other experimentally determined enthalpy changes. Some reactions are difficult, if not impossible, to investigate and make accurate measurements for experimentally. And even when a reaction is not hard to perform or measure, it is convenient to be able to determine the heat involved in a reaction without having to perform an experiment.

The Hinsberg test is a method to identify primary, secondary and tertiary amines, named after its pioneer, Oscar Hinsberg. Here, amines are treated with benzenesulfonyl chloride, also known as the Hinsberg reagent, in the presence of an excess of aqueous base, followed by acidification. Based on the nature of the amines, different changes are observed.
Generally, a primary amine reacts with the Hinsberg reagent to produce an N-substituted benzenesulfonamide. The electron-withdrawing sulfonyl...

The Frost circle or the inscribed polygon method is a graphical method for determining the relative energies of π molecular orbitals (MOs) for planar, fully conjugated, and monocyclic compounds. This method was first described by A. A. Frost and Boris Musulin in 1953.
A Frost circle is constructed by drawing a polygon whose number of edges is equal to the number of carbons of the given cyclic system, with one of the vertices pointing down. Then, a circle is drawn enclosing the polygon so that...

The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.

Salt stress—which can be triggered by high salt concentrations in a plant’s environment—can significantly affect plant growth and crop production by influencing photosynthesis and the absorption of water and nutrients.

The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.