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The p-stands for para-, indicating that the two methyl groups in p-xylene occupy the diametrically opposite substituent positions 1 and 4. It is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and m-xylene. All have the same chemical formula C 6 H 4 (CH 3) 2. All ...
Fractional crystallisation can be used to obtain pure para product, relying on the principle that it is less soluble than the ortho and thus will crystallise first. Care must be taken to avoid cocrystallisation of the ortho isomer. [2] Many nitro compounds' ortho and para isomers have quite different boiling points. These isomers can often be ...
Hess's law states that the change of enthalpy in a chemical reaction is the same regardless of whether the reaction takes place in one step or several steps, provided the initial and final states of the reactants and products are the same. Enthalpy is an extensive property, meaning that its value is proportional to the system size. [4]
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical reaction occurs. [1] A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of an overall chemical reaction. The detailed steps of a reaction are not observable in most cases.
For example, when 2-iodobutane is treated with alcoholic potassium hydroxide (KOH), but-2-ene is the major product and but-1-ene is the minor product. [1] More generally, Zaytsev's rule predicts that in an elimination reaction the most substituted product will be the most stable, and therefore the most favored.
The major product of the addition reaction will be the one formed from the more stable intermediate. Therefore, the major product of the addition of HX (where X is some atom more electronegative than H) to an alkene has the hydrogen atom in the less substituted position and X in the more substituted position.
In addition to the ordinary thermal phenyl ester reaction a photochemical variant is possible. The photo-Fries rearrangement can likewise give [1,3] and [1,5] products, [7] [8] which involves a radical reaction mechanism. This reaction is also possible with deactivating substituents on the aromatic group. Because the yields are low this ...
Methane chlorination is a chain reaction. If only the products and reactants are analyzed, the result is: CH 4 + 4 Cl 2 → CCl 4 + 4 HCl. However, this reaction has 3 intermediate reactants which are formed during a sequence of 4 irreversible second order reactions until we arrive at the final product. This is why it is called a chain reaction.