Statement 1 Rates of nitration of benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)\) and hexadeuterobenzene \(\left(\mathrm{C}_{6} \mathrm{D}_{6}\right)\) are identical if the same nitrating mixture is used at the same temperature. and Statement 2 \(\mathrm{C}-\mathrm{D}\) bond is stronger than \(\mathrm{C}-\mathrm{H}\) bond .

Understanding the electrophilic aromatic substitution (EAS) is crucial when studying organic reactions involving aromatic compounds like benzene. In EAS, an electrophile, a particle attracted to electrons, reacts with an aromatic system to replace one of the hydrogen atoms attached to the carbon atoms of the ring. This process typically occurs in several steps. First, the aromatic compound forms a complex with the electrophile, which increases the electrophile's reactivity. Next, the electrophile attacks the aromatic ring, causing a temporary loss of aromaticity as the ring takes on a positive charge, creating what we call an 'arenium ion' or 'sigma complex'.

The stability of this arenium ion is paramount to the reaction's completion, as it must be stable enough to lose a proton and regain its aromaticity. This stability is provided by the delocalization of the positive charge over the ring atoms in the form of resonance structures. The greater the stabilization by resonance, the more favorable the reaction will be. Resonance also allows the EAS reactions to occur despite benzene’s high stability, since the transition states and intermediates are energetically accessible.

Electrophilic aromatic substitution reactions are typical in organic chemistry and include common reactions like nitration, sulfonation, halogenation, acylation, and alkylation. Each involves its specific electrophile, but the underlying mechanism stays the same across the different types of EAS reactions.

The variation in bond strength between a carbon-hydrogen (C-H) bond and a carbon-deuterium (C-D) bond is a subtle, yet important concept in organic chemistry. Deuterium is an isotope of hydrogen which possesses an additional neutron, making it twice as heavy as a regular hydrogen atom. This increased mass leads to a lower vibrational frequency within the C-D bond compared to the C-H bond.

Lower vibrational frequencies result in lower zero-point energy levels, which contribute to a stronger bond in C-D compared to C-H. This phenomenon is derived from principles found in quantum mechanics and is referred to as the isotopic effect. Despite being stronger, the C-D bond still breaks in a fashion similar to the C-H bond during chemical reactions, unless the reactions are highly sensitive to the small differences in bond energies.

When we consider reactions like the nitration of benzene, the slightly greater strength of the C-D bond compared to the C-H bond might suggest a slower rate of reaction for the deuterated compound. However, since the nitration process involves an attack on the aromatic ring, rather than directly on the C-H or C-D bonds, the isotopic effect on the bond strength does not significantly impact the reaction rate in this case.

In many chemical reactions, particularly those involving multiple steps, intermediate species are formed. These intermediates are not the reactants or the products, but transient species that exist during the conversion from reactant to product. For a reaction to be viable, each step, including the formation and reformation of intermediates, must be energetically favorable. This is where the importance of reaction intermediate stabilization comes into play.

In electrophilic aromatic substitution reactions, such as the nitration of benzene, the generation of the arenium ion intermediate is a critical step. The stabilization of this intermediate plays a major role in the overall reaction kinetics. The arenium ion's stability arises from the distribution of positive charge across the aromatic ring through resonance. The more effectively this positive charge can be delocalized, the more stable the intermediate, and the more rapidly the reaction can proceed to its next steps.

If we look at the nitration of benzene compared to hexadeuterobenzene, despite the inherent difference in bond strengths between C-H and C-D, the reaction intermediate stabilization is similar for both. This is because the deuterium atoms do not significantly alter the delocalization of charge within the arenium ion, leading to comparable stability and reaction rates under identical conditions. Such insights highlight the complexity and the beauty of understanding how the stabilization of reaction intermediates influences the chemical reactions we observe.