Addition Reaction
An addition reaction is a chemical process in which two or more substances combine to form a single product. This reaction typically involves the breaking of multiple chemical bonds and the formation of new bonds. Addition reactions are commonly seen in organic chemistry, where they play a key role in the synthesis of various compounds.
3 Key excerpts on "Addition Reaction"
eBook - ePub- J Fisher, J.R.P. Arnold, Julie Fisher, John Arnold(Authors)
- 2020(Publication Date)
- Taylor & Francis(Publisher)
...In some instances, it is necessary to activate the potential leaving group to make it a better leaving group and thus promote the substitution reaction. Substitution reactions are a feature of carboxylic acid chemistry and aromatic chemistry. Elimination reactions Elimination reactions occur with the loss of (generally) a small neutral molecule, from a larger molecule. These reactions are common with alkyl halides and alcohols, leading, in each case, to the formation of alkenes. Oxidation and reduction processes In organic systems oxidation and reduction reactions are those that involve the gain or loss of oxygen, respectively. Reduction reactions can also involve the gaining of hydrogen; equivalent to the loss of oxygen. In many instances these processes involve free radicals. Oxidation and reduction reactions are features of the chemistry of almost all organic compounds, and are of great significance in biology. Related topics (A1) The periodic table (A2) Electron confguration Addition Reactions An Addition Reaction is said to have occurred when a molecule has combined with another, without the loss of any part (atom or groups of atoms) of either molecule. There are two general classes of Addition Reaction that may be considered, nucleophilic and electrophilic addition (Section I1). For either type of Addition Reaction to occur one or more units of unsaturation must be present in the molecule being added to. Consequently, Addition Reactions are only possible with, for example, alkenes, alkynes, aldehydes, and ketones...
eBook - ePub- Mukesh Doble, Anil Kumar Kruthiventi, Vilas Ganjanan Gaikar, Mukesh Doble, Anil Kumar Kruthiventi, Vilas Ganjanan Gaikar(Authors)
- 2004(Publication Date)
- CRC Press(Publisher)
...To add value is to profit. So, from the beginning, transformation was essential, whether in the making of metals and alloys, in medicinal preparations, in cooking, in dyeing and coloring, in tanning leather, or in the cosmetics. Reaction is fundamentally bringing about transformation. A directed reaction, which is a specific controlled reaction, can also be termed molecular engineering. Today, when a chemist thinks of a “reaction,” he or she sees both the macroscopic transformation as of old and the microscopic molecular change. Now we know, that in any chemical reaction the motions of the electrons and nuclei of atoms determine how the molecules interact and those interactions in turn create the forces that govern the reaction dynamics. 2.2.1 Basic Types of Reactions in Organic Chemistry At the molecular level a reaction starts when two molecules come close enough—within the bonding distance, approximately 0.1 nm—then they begin to interact. The electrons get rearranged; they start moving from an electron-rich center to an electron-deficient center. Transitory states are produced which either gets converted to the products or back to the reactants. These transitory states can be a transition state or an intermediate. Ahmed Zewail, a scientist from Caltech in the United States received the Nobel prize in chemistry (1999) for developing femtosecond laser photography to photograph these transitory states. The time scales for these transition states range from about 10 to 100 fs. A femtosecond is a very small unit of time. A femtosecond is to a second what a second is to 32 million years. Furthermore, while in 1 s light travels nearly 300,000 km—almost the distance between the earth and moon—in 1 fs light travels only 0.3 ìm—about the diameter of a smallest bacterium. When the movement/rearrangement of these electrons and nuclei is within the same molecule, it is termed an intramolecular reaction—similar to clasping of both the hands...
eBook - ePub- Dov M. Gabbay, Paul Thagard, John Woods, Dov M. Gabbay, Paul Thagard, John Woods(Authors)
- 2011(Publication Date)
- North Holland(Publisher)
...Of course, additional devices must be employed for more complicated reactions, but: “even such complicated mechanisms may be viewed as sequences of easily symbolized component processes” [ Guthrie, 1989, p. 25]. Now I will present an example of how the mechanism of a chemical reaction, or class of chemical reactions, is developed from the experimental evidence. 3. Establishing a Mechanism: The Bromonation of Alkenes An alkene is an organic molecule with a carbon-carbon double bond to which, in certain circumstances, it is possible to add two new substituents, one at each of the carbons in the original double bond. When the addition is carried out in a bromine solution (in the dark) it is known as a bromonation. The products of a bromonation typically have a bromine atom as either one or both of the new substituents. When it is not the case that both substituents are bromine, the second substituent is typically a derivative of the solvent in which the reaction is run. To give a specific example, stilbene (which is a carbon-carbon double bond with one phenyl group and one hydrogen on each side of the bond, see Figure 1) reacts with bromine (Br 2) dissolved in methanol to give almost exclusively a methoxy bromide product (where one substituent is bromine and the other is a methoxy group, derived from the solvent). It turns out that the amount of dibromide produced can be increased by adding bromide ions to the solution (Br −), but this has the additional consequence of slowing down the reaction. In one of the classic examples of how kinetics can be used to elucidate the mechanism of a reaction, [ Bartlett and Tarbell, 1936 ] argued that this Addition Reaction must be understood to involve two distinct addition steps, rather than one simultaneous addition to both sides of the double bond...
