Structure and Properties of Organic Molecules

The wedge bonds represent bonds coming out of the plane of the paper toward you. 

2-4 The hybridization of the nitrogen and the triple-bonded carbon are sp, giving linear geometry (C—C—N are linear) and a bond angle around the triple-bonded carbon of 180°. The CH3 carbon is sp hybridized, tetrahedral, with bond angles about 109°. 

2-7 For clarity, electrons in sigma bonds are not shown, (a) carbon and oxygen are both sp hybridized 

One pair of electrons on oxygen is always in an sp orbital. The other pair of electrons is shown in a p orbital in the first resonance form, and in a pi bond in the second resonance form. 

Resonance form A must be the major contributor. If B were the major contributor, the value of the charge separation would be between 0.5 and 1.0. Even though B is minor , it is quite significant, explaining in part the high polarity of the C=0. 

OI °f ozone shows that BOTH end oxygens must be sp — see Solved Problem 2-8) 

Both NH3 and NF3 have a pair of nonbonding electrons on the nitrogen. In NH3, the direction of polarization of the N—H bonds is toward the nitrogen thus, all three bond polarities and the lone pair polarity reinforce each other. In NF3, on the other hand, the direction of polarization of the N—F bonds is away from the nitrogen the three bond polarities cancel the lone pair polarity, so the net result is a very small molecular dipole moment. 

Q Predict the hybridization and geometry of organic e Predict general trends in physical properties such as 

Q Identify isomers and explain the differences Q Identify the general classes of organic compounds, 

Chapter 1 did not explain the actual shapes and properties of organic molecules. To understand these aspects of molecular structure we need to consider how the atomic orbitals on an atom mix to form hybrid atomic orbitals and how orbitals on different atoms combine to form molecular orbitals. In this chapter, we look more closely at how combinations of orbitals account for the shapes and properties we observe in organic molecules. 

A standing wave. The fundamental frequency of a guitar string is a standing wave with the string alternately displaced upward and downward. 

We like to picture the atom as a miniature solar system, with the electrons orbiting around the nucleus. This solar system picture satisfies our intuition, but it does not accurately reflect today s understanding of the atom. About 1923, Louis de Broglie suggested that the properties of electrons in atoms are better explained by treating the electrons as waves rather than as particles. 

The waveform of a U orbital is like this guitar string, except that it is three-dimensional. The orbital can be described by its wave function, ijf, which is the mathematical description of the shape of the wave as it vibrates. All of the wave is positive in sign for a brief instant then it is negative in sign. The electron density 

The U orbital. The Is orbital is similar to the fundamental vibration of a guitar string. The wave function is instantaneously all positive or all negative. The square of the wave function gives the electron density. A circle with a nucleus is used to represent the spherically symmetrical s orbital. 

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The coverage is also more broad in terms of chemistry . For the most part, "Ab Initio Molecular Orbital Theory focused on the structures and properties of organic molecules, accessible at that time... 

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