Methyl isocyanate, \(\mathrm{CH}_{3} \mathrm{NCO},\) was made infamous in 1984 when an accidental leakage of this compound from a storage tank in Bhopal, India, resulted in the deaths of about 3800 people and severe and lasting injury to many thousands more. (a) Draw a Lewis structure for methyl isocyanate. (b) Draw a ball-and-stick model of the structure, including estimates of all the bond angles in the compound. (c) Predict all the bond distances in the molecule. (d) Do you predict that the molecule will have a dipole moment? Explain.

First, count the total number of valence electrons for the molecule. Carbon (C) has 4, Nitrogen (N) has 5, Oxygen (O) has 6, and Hydrogen (H) has 1 valence electron each. In the CH3NCO molecule, there are 3 Hydrogen atoms, so the total number of valence electrons is 4 (from C) + 5 (from N) + 6 (from O) + 3 * 1 (from the 3 H atoms) = 16. Now, arrange the atoms and distribute the electrons: 1. Place the central atom (Carbon) in the center. 2. Place the other atoms around it (N next to C, O next to N, and the 3 H atoms around the central C). 3. Distribute the electrons by placing pairs between the atoms to form single bonds. Add remaining electrons as lone pairs. 4. Make multiple bonds if needed to satisfy the octet rule for all atoms except Hydrogen. The Lewis structure of methyl isocyanate is: H | H--C--N==C==O | H

To draw a ball-and-stick model, represent each atom as a sphere connected by sticks indicating the bonds. You can estimate the bond angles based on the molecular geometry and the bond pair repulsion theory. For methyl isocyanate: 1. The central Carbon atom is surrounded by three groups (three Hydrogen atoms) with a tetrahedral molecular geometry. The H-C-H bond angle is approximately 109.5°. 2. Nitrogen and Oxygen atoms are involved in a double bond with the Carbon atom. The N-C-O bond angle is approximately 180° since NCO has a linear geometry. The ball-and-stick model of methyl isocyanate with the bond angles will look like the following: H | H--C--N==C==O (180°) | H (109.5°)

To predict bond distances, you can use known bond lengths for similar chemical species: 1. C-H bond: The bond length in methyl isocyanate is expected to be the same as in other aliphatic hydrocarbons, approximately 1.09 Å. 2. C-N bond: The bond length in methyl isocyanate is expected to be similar to a C-N single bond length, which is approximately 1.47 Å. 3. N=C double bond: The bond length in methyl isocyanate is expected to be similar to a N=C double bond length, which is approximately 1.24 Å. 4. C=O double bond: The bond length in methyl isocyanate is expected to be similar to a C=O double bond length, which is approximately 1.21 Å.

A molecule has a dipole moment when there is a difference in electronegativity and an asymmetric distribution of charge. In methyl isocyanate, the C-N bond and the N=C bond are polar due to a difference in electronegativity between Carbon and Nitrogen. The C=O bond is also polar due to a difference in electronegativity between Carbon and Oxygen. However, since the NCO group in the molecule is linear, the bond dipoles of the N=C and C=O bonds are pointing in opposite directions and therefore cancel each other out. As a result, the net dipole moment of the molecule is due to the C-N bond and the three C-H bonds creating a slight asymmetry in the electron distribution. Therefore, methyl isocyanate does have a dipole moment.