A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or destroyed in a chemical reaction—the same type and number of atoms that make up the reactants are still present in the products. Merely, the rearrangement of chemical bonds produces new compounds.
Chemical Reactions Rearrange Atoms into New Substances
A chemical reaction takes starting materials—the reactants—and changes them into different...

The status of a reversible reaction is conveniently assessed by evaluating its reaction quotient (Q). For a reversible reaction described by m A + n B ⇌ x C + y D, the reaction quotient is derived directly from the stoichiometry of the balanced equation as

Another method of radical formation is the elimination process. It is the opposite of the addition route and is driven by the instability of the radical. For example, as depicted in Figure 1, dibenzoyl peroxide yields a pair of unstable radicals upon homolysis. Given its instability, this radical spontaneously undergoes elimination via a C–C bond cleavage to form a relatively more stable phenyl radical. The mechanism involves cleavage of the bond between the α and β positions with respect to...

Consecutive reactions involve a sequence where the product of a preceding reaction becomes the reactant for the subsequent one. In a simple scheme, A transforms into B, which further reacts to form C, with rate constants k1 and k2, respectively. This concept is evident in the radioactive decay series. Assuming an initial state with only A present, the conservation of matter leads to three coupled differential equations, determining the concentrations of A, B, and C over time.The rate of change...

Reversible or opposing reactions play a crucial role in understanding the dynamic nature of chemical processes. While kinetics focuses on how reactions proceed, thermodynamics emphasizes that most reactions do not reach completion. Instead, a reverse reaction starts occurring over time, and when its rate equals that of the forward reaction, a dynamic equilibrium is established.For example, consider a simple chemical process where A forms B reversibly. The rate constants for the forward and...

Phase I biotransformation reductive reactions are chemical processes that modify drugs by introducing or revealing polar functional groups via reduction. Enzymes called reductases catalyze these reactions, playing a pivotal role in drug metabolism by transforming lipophilic drugs into more polar, water-soluble metabolites for easy excretion. An essential type of reductive reaction is the carbonyl group reduction, where aldehydes and ketones are reduced to alcohols. An example is the...