The correct sequence of bond enthalpy of ‘C–X’ bond is
The correct sequence of bond enthalpy of ‘C–X’ bond is
CH3−Cl > CH3−F > CH3−Br > CH3−I
CH3−F < CH3−Cl < CH3−Br < CH3−I
CH3−F > CH3−Cl > CH3−Br > CH3−I
CH3−F < CH3−Cl > CH3−Br > CH3−I
The Correct Option is C
Solution and Explanation
To determine the correct sequence of bond enthalpy for the ‘C–X’ bond in methyl halides, we must understand the concept of bond enthalpy, which is the measure of bond strength in a chemical bond.
Bond Enthalpy Explanation: Bond enthalpy is the energy required to break one mole of bonds in gaseous molecules. A higher bond enthalpy indicates a stronger bond. The bond enthalpy of a C–X bond decreases as we move down the halogen group (F, Cl, Br, I) due to increased atomic size and decreased electronegativity.
Comparison of C–X Bonds:
- CH_3-F: The C–F bond is the strongest among methyl halides due to the high electronegativity and small size of fluorine.
- CH_3-Cl: The C–Cl bond is weaker than C–F but stronger than C–Br and C–I.
- CH_3-Br: The C–Br bond is weaker due to the larger size of bromine compared to chlorine.
- CH_3-I: The C–I bond is the weakest due to the largest size of iodine, leading to the longest bond length.
From this understanding, the correct sequence of bond enthalpies is:
CH_3-F > CH_3-Cl > CH_3-Br > CH_3-I
Conclusion: The correct answer is CH3−F > CH3−Cl > CH3−Br > CH3−I because bond strength decreases as the size of the halogen increases. This trend matches the provided option and confirms our understanding of bond enthalpies in methyl halides.
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Concepts Used:
Haloalkanes and Haloarenes - Nomenclature
Nomenclature of Haloalkanes:
‘Alkyl halide’ is the very common name for haloalkanes. The written format for haloalkane in the IUPAC name is “numerical position-alphabetically placed halo- root-word-ane”
Nomenclature of Haloarenes:
‘Aryl Halide’ is the very common name for haloarenes. In the nomenclature system, the numerical prefixes are named, depending on the basic position of the halogen atom in the aromatic ring.
In presence of more than one halogen atom, the halogen group is named and the aromatic ring is numbered based on the numerical position of the aromatic ring. Numerical prefixes are written in the format (1, 2) ; (1,3) ; (1,4). Always the least number is given to the halogen number.
Read More: Nomenclature of Haloalkanes and Haloarenes
Nomenclature of Haloalkanes and Haloarenes