Search results
Results From The WOW.Com Content Network
Reaction Sequences: Multistep synthesis involves sequential chemical reactions, each requiring its own work-up to isolate intermediates before proceeding to the next stage. [ 4 ] For example, the synthesis of paracetamol typically requires three separate reactions.
Using the twenty natural amino acids, for example, in a tripeptide creates 8,000 (20 3) possibilities. Solid-phase methods for small molecules were later introduced and Furka devised a "split and mix" approach [2] [4] In its modern form, combinatorial chemistry has probably had its biggest impact in the pharmaceutical industry. [5]
The general form of a direct combination reaction is: A + B → AB. where A and B are elements or compounds, and AB is a compound consisting of A and B. Examples of combination reactions include: 2Na + Cl 2 → 2NaCl (formation of table salt) S + O 2 → SO 2 (formation of sulfur dioxide) 4Fe + 3O 2 → 2Fe 2 O 3 (iron rusting)
One example of a synthesis reaction is the combination of iron and sulfur to form iron(II) sulfide: + Another example is simple hydrogen gas combined with simple oxygen gas to produce a more complex substance, such as water.
The Ugi reaction has been applied in combination with an intramolecular Diels-Alder reaction [16] in an extended multistep reaction. A reaction in its own right is the Ugi–Smiles reaction with the carboxylic acid component replaced by a phenol. In this reaction the Mumm rearrangement in the final step is replaced by the Smiles rearrangement. [17]
Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature". [6]
These reactions are exothermic and the rise in temperature is usually in the order of the reactivity of the different metals. [5] If the reactant in elemental form is not the more reactive metal, then no reaction will occur. Some examples of this would be the reverse. + No Reaction
For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H 2 O. In the case of non-stoichiometric compounds , the proportions may be reproducible with regard to their preparation, and give fixed proportions of their component elements, but proportions that are not integral [e.g., for palladium ...