Question

A compound with highest dipole moment value is (A) \(\mathrm{CH}_{3}-\mathrm{F}\) (B) \(\mathrm{CH}_{3}-\mathrm{Cl}\) (C) \(\mathrm{CH}_{3}-\mathrm{Br}\) (D) \(\mathrm{CH}_{2}-\mathrm{I}\)

Short answer

The compound with the highest dipole moment value is (A) \(\mathrm{CH}_{3}-\mathrm{F}\), as it has the highest electronegativity difference (1.43) among the given compounds.

Step-by-step solution

Recall the definition of dipole moment

Dipole moment (\(\mu\)) in a molecule arises due to the difference in electronegativity between two atoms, causing a separation of positive and negative charges. Higher electronegativity difference between bonding atoms results in higher dipole moment.

Gather electronegativity values

We need to gather the electronegativity values for the atoms involved in the given compounds. Electronegativity values: - Carbon (C): 2.55 - Hydrogen (H): 2.20 - Fluorine (F): 3.98 - Chlorine (Cl): 3.16 - Bromine (Br): 2.96 - Iodine (I): 2.66

Calculate electronegativity difference in each compound

Now, let's calculate the electronegativity difference between the central atom (Carbon) and the different halogens in each compound. (A) \(\mathrm{CH}_{3}-\mathrm{F}\): \(|\)3.98 - 2.55\(|\) = 1.43 (B) \(\mathrm{CH}_{3}-\mathrm{Cl}\): \(|\)3.16 - 2.55\(|\) = 0.61 (C) \(\mathrm{CH}_{3}-\mathrm{Br}\): \(|\)2.96 - 2.55\(|\) = 0.41 (D) \(\mathrm{CH}_{2}-\mathrm{I}\): \(|\)2.66 - 2.55\(|\) = 0.11

Determine which compound has the highest dipole moment

The compound with the highest electronegativity difference will have the highest dipole moment. Comparing the electronegativity differences calculated in the previous step, we can see that the compound (A) \(\mathrm{CH}_{3}-\mathrm{F}\) has the highest electronegativity difference (1.43). Therefore, the compound with the highest dipole moment value is: (A) \(\mathrm{CH}_{3}-\mathrm{F}\)

Key concepts

Electronegativity

Electronegativity is a fundamental concept in understanding many aspects of organic chemistry, especially when it comes to predicting the behavior of molecules. It can be described as an atom's ability to attract and hold onto electrons. This property varies across the periodic table, with some elements like fluorine having a high electronegativity, while others such as cesium have low values.

When atoms with different electronegativities bond together, an unequal sharing of electrons occurs because the more electronegative atom has a stronger pull for the electrons. As a result, the less electronegative atom becomes slightly positive, and the more electronegative atom becomes slightly negative, creating a dipole moment in the compound.

In the context of organic molecules, the presence of highly electronegative atoms, like oxygen or halogens, can greatly affect the compound's physical and chemical properties. Understanding how electronegativity influences molecular interactions is crucial for predicting reactivity and the formation of chemical bonds.

Molecular Polarity

Molecular polarity arises from the presence of dipole moments within the molecule, which are caused by an uneven distribution of electron density. The polarity of a molecule can influence its solubility, melting point, boiling point, and reactivity. Polar molecules have a significant difference in electronegativity between the atoms involved in a bond, leading to partial charges within the molecule.

This separation of charge allows polar molecules to interact with other polar substances through dipole-dipole interactions and hydrogen bonding. For example, water (H_{2}O) is a polar molecule because of the significant difference in electronegativity between hydrogen and oxygen, enabling it to dissolve many polar compounds. When analyzing organic structures, recognizing polar bonds and the overall molecule's polarity is essential for understanding its behavior in different environments and interactions with other molecules.

Halogenated Organic Compounds

Halogenated organic compounds contain at least one halogen atom (fluorine, chlorine, bromine, or iodine) attached to the carbon skeleton of the organic molecule. These halogens are highly electronegative and can profoundly impact the compound's physical and chemical properties by inducing polarity.

In the educational exercise, halogenated compounds were considered to evaluate their dipole moment. The greater the electronegativity of the halogen, the more polar the bond it forms with carbon. This explains why a molecule such as CH_{3}-F, where fluorine is the most electronegative element, has a significantly higher dipole moment compared to other halogenated compounds like CH_{3}-Cl, CH_{3}-Br and CH_{2}-I. Such insights into molecular structure and bond polarity are especially important when determining reactivity, toxicity, and environmental impact of halogenated organic compounds.