what type of reaction occurs to form a dipeptide
peptide bond
title: Chemical reaction text: The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. Examples of nucleophiles are hydroxide ion, alkoxides, amines and halides. This type of reaction is found mainly in aliphatic hydrocarbons, and rarely in aromatic hydrocarbon. The latter have high electron density and enter nucleophilic aromatic substitution only with very strong electron withdrawing groups. Nucleophilic substitution can take place by two different mechanisms, S1 and S2. In their names, S stands for substitution, N for nucleophilic, and the number represents the kinetic order of the reaction, unimolecular or bimolecular. The S1 reaction proceeds title: Pericyclic reaction text: pericyclic reactions are given in the table below (the three most important classes are shown in bold). Ene reactions and cheletropic reactions are often classed as group transfer reactions and cycloadditions/reversions, respectively, while dyotropic reactions and group transfer reactions (if ene reactions are excluded) are rarely encountered. In general, these are considered to be equilibrium processes, although it is possible to push the reaction in one direction by designing a reaction by which the product is at a significantly lower energy level; this is due to a unimolecular interpretation of Le Chatelier's principle. There is thus a set of "retro" title: Chemical reaction text: For bimolecular reactions, two molecules collide and react with each other. Their merger is called chemical synthesis or an addition reaction. Another possibility is that only a portion of one molecule is transferred to the other molecule. This type of reaction occurs, for example, in redox and acid-base reactions. In redox reactions, the transferred particle is an electron, whereas in acid-base reactions it is a proton. This type of reaction is also called metathesis. for example Most chemical reactions are reversible, that is they can and do run in both directions. The forward and reverse reactions are competing with each title: Elimination reaction text: or through Hofmann elimination if the carbon with the most substituted hydrogen is inaccessible. During the 1920s, Sir Christopher Ingold proposed a model to explain a peculiar type of chemical reaction: the E2 mechanism. E2 stands for bimolecular elimination. The reaction involves a one-step mechanism in which "carbon-hydrogen" and "carbon-halogen" bonds break to form a double bond ("C=C Pi bond"). The specifics of the reaction are as follows: An example of this type of reaction in "scheme 1" is the reaction of isobutylbromide with potassium ethoxide in ethanol. The reaction products are isobutylene, ethanol and potassium bromide. E1 is a title: Chemical reaction text: temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms. Reactions may proceed in the forward or reverse direction until they go to completion or reach equilibrium. Reactions that proceed in the forward direction to approach equilibrium are often described as spontaneous, requiring no input of free energy to go forward. Non-spontaneous reactions require input of free energy to go forward (examples include charging a battery by applying an external electrical power source, or photosynthesis driven by absorption of electromagnetic radiation in the form of sunlight). Different chemical reactions are used