List of top Chemistry Questions

The correct option(s) of reagents and reaction sequences suitable for carrying out the following transformation is/are 

Consider the following two reactions and their corresponding Hammett plots

The complex(es) having metal-metal bond order \( \ge 3.5 \) is/are [Given: The atomic numbers of Mo, Cr, Mn, and Re are 42, 24, 25, and 75, respectively.]

Cytochrome P450 (CYP) enzymes catalyze stereoselective C-H hydroxylation of hydrocarbons in the presence of O\( _2 \). The correct statement(s) about the structure and activity of CYP is/are

The UV-visible spectrum of [Ni(en)\(_3\)]\(^{2+}\) (en = ethylenediamine) shows absorbance maxima at 11200 cm\(^{-1}\), 18350 cm\(^{-1}\), and 29000 cm\(^{-1}\). 

[Given: Atomic number of Ni = 28] The correct match(es) between absorbance maximum and electronic transition is/are

The compound(s) having structure similar to that of B\( _2 \)H\( _6 \) is/are

An approximate partition function \(Q(N, V, T)\) of a gas is given below. \[ Q(N, V, T) = \frac{1}{N!} \left( \frac{2 \pi m k_B T}{h^2} \right)^{3N/2} (V - Nb)^N \] The equation of state(s) for this gas is/are [Note: \(b\) is a parameter independent of volume.]

The correct option with regard to the following statements is 
(a) Time-independent Schrödinger equation can be exactly solved for Be\(^{2+}\). 
(b) For a particle confined in a one-dimensional box of length \( l \) with infinite potential barriers, the trial variation function \( \phi = \left[ \left( \frac{3}{l^3} \right)^{1/2} x \right] \) is not an acceptable trial wavefunction for \( 0 \le x \le l \). 
(c) Wavefunctions for system of Fermions must be anti-symmetric with respect to exchange of any two Fermions in the system. 
(d) Born-Oppenheimer approximation can be used to separate the vibrational and rotational motion of a molecule.

In the following asymmetric transformation, the key aldol reaction involves the attack of 

The major product formed in the following reaction sequences is: 

Compound K displayed a strong band at 1680 cm−1 in its IR spectrum. Its 1H-NMR spectral data are as follows:

δ (ppm):
7.30 (d, J = 7.2 Hz, 2H)
6.80 (d, J = 7.2 Hz, 2H)
3.80 (septet, J = 7.0 Hz, 1H)
2.20 (s, 3H)
1.90 (d, J = 7.0 Hz, 6H)

The correct structure of compound K is:

The major products X and Y formed in the following reaction sequences are:

The effective magnetic moment, μeff, value for [Cr(H2O)6]3+ taking into account spin–orbit coupling is closest to:

[Given: Atomic number of Cr = 24, spin–orbit coupling constant λ = 92 cm−1, and Δo = 17400 cm−1]

The 1H NMR spectrum of the given iridium complex at room temperature gave a single signal at 2.6 ppm, and its 31P NMR spectrum gave a single signal at 23.0 ppm. When the spectra were recorded at lower temperatures, both these signals split into a complex pattern. The intra-molecular dynamic processes shown by this molecule are: 

 

The given zirconocene compound, (η5-Cp)2ZrEt2, when heated in the presence of an equimolar amount of PMe3 results in the formation of a compound X which obeys the 18-electron rule. The reaction also resulted in the release of a saturated hydrocarbon.

[Given: Atomic number of Zr = 40]

The structure of compound X is:

The homogeneous catalyst whose metal ion does NOT undergo either oxidation or reduction in any of the steps during the hydrogenation of terminal olefins is:

The reaction that proceeds through an oxidative addition followed by a reductive elimination is:

[Given: Atomic numbers Ni = 28, Ta = 73, Zr = 40, Pt = 78]

The expressions for the vapour pressure of solid (\( p_1 \)) and vapour pressure of liquid (\( p_2 \)) phases of a pure substance, respectively, are \[ \ln p_1 = \frac{-2000}{T} + 5 \quad {and} \quad \ln p_2 = \frac{-4000}{T} + 10 \] The triple point temperature of this substance is ________ K (in integer).}

The ratio of the fundamental vibrational frequencies \( \left( \nu_{^{13}C^{16}O} / \nu_{^{12}C^{16}O} \right) \) of two diatomic molecules \( ^{13}C^{16}O \) and \( ^{12}C^{16}O \), considering their force constants to be the same, is ___________ (rounded off to two decimal places).}

The specific rotation of enantiomerically pure (S)-2-butanol is \( +14^\circ \). The specific rotation of the enantiomeric mixture of 2-butanol obtained from an asymmetric reduction of 2-butanone is found to be \( +7^\circ \).

The percentage of (R)-2-butanol present in the reaction mixture is _________ (in integer).

Partial hydrolysis of a pentapeptide yields all possible tripeptides and dipeptides. The dipeptides that are obtained upon hydrolysis are given below:

  • Val–Ala
  • Gln–His
  • Phe–Val
  • Ala–Gln

The total number of tripeptides obtained that contain ‘Ala’ as one of the amino acids is 2 (in integer).

The total number of hyperfine lines expected in the EPR spectrum of •CH2OH (radical) is ___________ (in integer).

Xe and F2 in 1:1 molar ratio when mixed in a closed flask and kept in sunlight for a day, gave white crystals of a compound Q. Two equivalents of Q on reaction with one equivalent of AsF5 gave an ionic compound X+Y– with the cation having two Xe atoms. The total number of lone pairs present on the cation X+ is ___________ (in integer).

The thermodynamic criterion/criteria for a spontaneous process is/are
Consider two non-interacting particles confined to a one-dimensional box with infinite potential barriers. Their wavefunctions are \( \psi_1 \) and \( \psi_2 \), and energies are \( E_1 \) and \( E_2 \), respectively. The INCORRECT statement(s) about this system is/are: