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The phase rule, also known as the Gibbs phase rule, relates the number of components and the number of degrees of freedom in a system at equilibrium by the formula \[F = C - P + 2 \tag{1}\]
Orthogonal protection is a strategy allowing the deprotection of multiple protective groups one at a time each with a dedicated set of reaction conditions without affecting the other. It was introduced in the field of peptide synthesis by Robert Bruce Merrifield in 1977.
The number of degrees of freedom (number of variables we can change without affecting the nature of the system) is determined by the equation known as the phase rule: p + 2, (6.2) where f is the no. of degrees of freedom, p is the number of phases present and the. 2 represents the two variables temperature and pressure.
Figure 3.5 is a schematic diagram of an experiment taken from Hildebrand (1970), which shows seven phases in equilibrium at near-ambient temperature. The phase on top is air, followed by six liquid phases in order of increasing density: hexane-rich, aniline-rich, water-rich, phosphorous, gallium and mercury.
Quantitative protection and deprotection can be achieved using reagents that form strong bonds and thus drive the reactions forward by a favorable change in enthalpy. Alternatively, liberation of gases can provide the required increase in total entropy, and thus drive the reaction to completion.
16 Δεκ 2021 · The phase rule is an important generalization dealing with the behavior of the heterogeneous system. It is possible to predict qualitatively by means of a diagram the effect of changing pressure, temperature, and concentration at equilibrium.
J. Kocienski, Protecting Groups, Georg Thieme Verlag, 1994 1. Hydroxyl groups 2 Ketones and aldehydes 3. Amines 4. Carboxylic Acids - Protect functional groups which may be incompatible with a set of reaction conditions - 2 step process- must be efficient - Selectivity a. selective protection b. selective deprotection.
