The conversion(s) that can be carried out by bromine in carbon tetrachloride solvent is/are
- PhCH=CHCH3\(\rightarrow\)PhCHBrCHBrCH3
- CH3CH2COOH\(\rightarrow\)CH3CHBrCOOH
The Correct Option is A, D
Solution and Explanation
There are two common qualitative methods used to test for unsaturation in compounds: the reaction with bromine in carbon tetrachloride and the reaction with potassium permanganate. In both cases, a positive result is indicated by the fading of the reagent's color.
In the bromine in carbon tetrachloride test, alkenes (with C=C) and alkynes (with C≡C) react with bromine to form dibromo- or tetrabromo-compounds. This uses up molecular bromine, which causes the dark red-brown color to fade. Thus, rapid disappearance of the bromine color confirms unsaturation.
The Baeyer test uses potassium permanganate ($\text{KMnO}_4$), an oxidizing agent. It oxidizes:
- Alkenes to glycols (alkanediols)
- Alkynes to carboxylic acids
In both cases, the purple color of $\text{KMnO}_4$ fades, indicating a positive test.
Only ethene (an alkene) shows positive results in both tests. Ethane (a saturated hydrocarbon) does not react.
So, the correct answer is option(s):
(A): $ \text{PhCH=CHCH}_3 \rightarrow \text{PhCHBrCHBrCH}_3 $ (positive bromine test)
(D):
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Concepts Used:
Alkanes
In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carbon-carbon bonds are single. Alkanes have the general chemical formula CnH2n+2. The alkanes range in complexity from the simplest case of methane (CH4), where n = 1 (sometimes called the parent molecule), to arbitrarily large and complex molecules, like pentacontane (C50H102) or 6-ethyl-2-methyl-5-(1-methylethyl) octane, an isomer of tetradecane (C14H30).
Alkane as saturated hydrocarbons:
- Alkanes are a series of compounds that contain carbon and hydrogen atoms with single covalent bonds. These are known as saturated hydrocarbons. This group of compounds consists of carbon and hydrogen atoms with single covalent bonds. Also comprises a homologous series having a molecular formula of CnH2n+2.
- Alkanes are the simplest family of hydrocarbons. They contain only carbon and hydrogen. Each carbon atom forms four bonds and each hydrogen atom forms one bond. Chemists use line-angle formulas because they are easier and faster to draw than condensed structural formulas. Structural formulas for alkanes can be written in yet another condensed form.
Properties of Alkanes:
1. The Solubility of Alkanes
Due to very little difference of electronegativity between carbon and hydrogen and covalent nature of C-C bond or C-H bond, alkanes are generally non-polar molecules.As we generally observe, polar molecules are soluble in polar solvents whereas non-polar molecules are soluble in non-polar solvents. Hence, alkanes are hydrophobic in nature that is, alkanes are insoluble in water.
2. The Boiling Point of Alkanes
As the intermolecular Van Der Waals forces increase with the increase of the molecular size or the surface area of the molecule we observe:The straight-chain alkanes are observed to have a higher boiling point in comparison to their structural isomers.
3. The Melting Point of Alkanes
The melting point of alkanes follow the same trend as their boiling point that is, it increases with increase in molecular weight.