Concept explainers
(a)
Interpretation:
The orbital picture of
Concept introduction:
Orbital picture of a molecule can be built up by first determining which orbitals will overlap and interact effectively. These are generally the orbitals from the valence shell of the atoms forming the bonds; mostly s and p orbitals. The orbital that will overlap end-on and the ones that overlap sideways are then determined on the basis of the electron geometry of the atoms. End on overlap leads to
(b)
Interpretation:
The total number of MOs of
Concept introduction:
Sideways interaction of AOs produces MOs of
The number of MOs produced is same as the number of contributing AOs.
(c)
Interpretation:
The orbital energy diagram for CO is to be drawn and the HOMO and LUMO identified.
Concept introduction:
The molecular orbital energy diagram of a molecule is built up by considering the interactions of all the valence shall orbitals from each atom. The total number of MOs produced is the same as the number of interacting AOs.
An end-on overlap of two orbitals produces a pair of MOs of
Interactions between p orbitals produces MOs of two types, one pair with a
The valence electrons of the contributing atoms are then filled in these MOs in increasing order of energy. The MO of highest energy that contains any electrons is called the highest occupied molecular orbital (HOMO), and the empty MO immediately above it is called the lowest unoccupied molecular orbital (LUMO).
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Chapter 3 Solutions
Organic Chemistry: Principles and Mechanisms (Second Edition)
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- a) Consider a molecule of acetone cyanohydrin, shown below. What is the hybridization and molecular geometry at CA, CB, and O? (b) For Carbon B (CB) and nitrogen (N), draw orbital energy diagrams showing the orbitals involved in bonding after hybridization. Be sure to fill the orbitals appropriately with valence electrons. c) In your diagrams in part (b), which orbitals are involved in sigma and pi bonding? Orbitals Involved in Sigma Bonding Orbitals Involved in Pi Bonding 2p sp sp2 sp3 2p sp sp2 sp3 (d) In a sample containing many molecules of acetone cyanohydrin (and no other substances), what type(s) of intermolecular forces could be present? Choose all that apply. Covalent Bonds Hydrogen Bonds Dipole-Dipole Forces London Dispersion Forcesarrow_forwardThe ground-state electron configuration of the H; molec- ular ion is (og15)'. (a) A molecule of H absorbs a photon, promoting the electron to the os molecular orbital. Predict what happens to the molecule. (b) Another molecule of H absorbs even more energy promoting the electron to the o,2, molecular orbital. Predict what happens to this molecule.arrow_forwardThe following is part of a molecular orbital energy-level diagramfor MOs constructed from 1s atomic orbitals. (a) What labels do we use for the two MOs shown? (b) Forwhich of the following molecules or ions could this be theenergy-level diagram:H2, He2, H2+, He2+, or H2-?(c) What is the bond order of the molecule or ion? (d) If anelectron is added to the system, into which of the MOs will itbe added? [arrow_forward
- (a) What is the difference between a localized p bond and adelocalized one? (b) How can you determine whether a moleculeor ion will exhibit delocalized p bonding? (c) Is the pbond in NO2- localized or delocalized?arrow_forward(a) Sketch the molecular orbitals of the H2- ion and draw itsenergy-level diagram. (b) Write the electron configuration ofthe ion in terms of its MOs. (c) Calculate the bond order inH2-. (d) Suppose that the ion is excited by light, so that anelectron moves from a lower-energy to a higher-energy molecularorbital. Would you expect the excited-state H2- ion to bestable? (e) Which of the following statements about part (d) is correct: (i) The light excites an electron from a bonding orbitalto an antibonding orbital, (ii) The light excites an electronfrom an antibonding orbital to a bonding orbital, or (iii)In the excited state there are more bonding electrons thanantibonding electrons?arrow_forwardTOPIC: QUANTUM, ATOMIC AND MOLECULAR PHYSICIS (a) Using Hückel's method, describe the energy of the molecular orbitals T of cyclobutadiene C4H4, which is a flat molecule made up of a square ring of carbons, as shown in the figure; (b) Do the same for 1,3-butadiene C4H6, which is an elongated planar molecule, as shown in the figure. (c) In both cases, draw an energy diagram indicating the filling of the orbitals and identifying the HOMO and the LUMO. Sketch by hand schematically (using two colors to distinguish the lobes from the 2pz orbitals) the result obtained for the orbitals, identifying them with the corresponding energy. If possible, you can use the Orbital Viewer program to plot the orbitals.arrow_forward
- Hybridization. (a) For acetone (shown below), give the electronic configuration as a function of energy and show how the orbitals are modified to explain sp² hybridization on the carbonyl oxygen. (b) Place the appropriate number of electrons into the hybridized orbitals to explain the bonding (geometry and types of orbitals) around the oxygen atom. (c) Describe the bonding to justify the sp² hybridization of the oxygen atom. I Carrow_forwardFor each of these contour representations of molecular orbitals,identify (a) the atomic orbitals (s or p) used to constructthe MO (b) the type of MO (s or p), (c) whether the MO isbonding or antibonding, and (d) the locations of nodalplanes.arrow_forwarda.) Give the bond order of Li2 ,Be2 ,C2 b.) Give the ground state electron configurations ofCO,NO ,CN- .The gerade and ungerade designation is technically not appropriate for heteronuclear diatomics, but rather use the "*" after S or P to represent antibonding. Still, S would stand for σ. Let P represent a pair of π MO's. Enclose each MO in parenthesis followed by the number of electrons in that MO, e.g., the entry (1S*)2 would represent 1σ* 2.arrow_forward
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