Molecule line-bond structures

Draw a line-bond structure for propane, CH3CH2CH3. Predict the value of each bond angle, and indicate the overall shape of the molecule. 

Draw the following molecule as a line-bond structure, and show how it can be prepared from a ketone and an amine. 

Line-bond structure (Section 1.5) A representation of a molecule showing covalent bonds as lines between atoms. 

Molecule Electron-dot structure Line-bond structure... 

To save space, molecules are shown as line-bond structures with lone pairs, rather than as electron-dot structures. 

Draw line-bond structures for the following molecules ... 

The best way to think about resonance forms is to realize that a molecule like nitromethane is no different from any other. Nitromethane doesn t jump hack and forth between two resonance forms, spending part of its time looking like one and the rest of its time looking like the other. Rather, nitromethane has a single unchanging structure that is a resonance hybrid of the two individual forms and has characteristics of both. The only problem with nitromethane is that we can t draw it accurately using a familiar Kekule line-bond structure. Line-bond structures just don t work well for resonance hybrids. The difficulty, however, lies with the representation of nitromethane on paper, not with nitromethane itself. 

ChemSketch has some special-purpose building functions. The peptide builder creates a line structure from the protein sequence defined with the typical three-letter abbreviations. The carbohydrate builder creates a structure from a text string description of the molecule. The nucleic acid builder creates a structure from the typical one-letter abbreviations. There is a function to clean up the shape of the structure (i.e., make bond lengths equivalent). There is also a three-dimensional optimization routine, which uses a proprietary modification of the CHARMM force field. It is possible to set the molecule line drawing mode to obey the conventions of several different publishers. 

Organic molecules are usually drawn using either condensed structures or skeletal structures. In condensed structures, carbon-carbon and carbon-hydrogen bonds aren t shown. In skeletal structures, only the bonds and not the atoms are shown. A carbon atom is assumed to be at the ends and at the junctions of lines (bonds), and the correct number of hydrogens is menially supplied. 

Bond structure can also be represented by lines. Each electron pair is shown by a line. In other words two electrons are shown by a line So the line representation of the fluorine molecule is IF—FI. The line between the two fluorine atoms represents the bond. Sometimes both the Lewis symbol and line representation can be used in the same molecule. For example, the F2 molecule can also be represented as F— F ... 

Show the bond structure of the nitrogen molecule by using an orbital diagram, electron dot structure and line representation. 

Show the bond structure of the oxygen molecule by using orbital, electron dot and line representations. 

Many molecules that have several double bonds are much less reactive than might be expected. The reason for this is that the double bonds in these structures cannot be localized unequivocally. Their n orbitals are not confined to the space between the double-bonded atoms, but form a shared, extended Tu-molecular orbital. Structures with this property are referred to as resonance hybrids, because it is impossible to describe their actual bonding structure using standard formulas. One can either use what are known as resonance structures—i. e., idealized configurations in which n electrons are assigned to specific atoms (cf pp. 32 and 66, for example)—or one can use dashed lines as in Fig. B to suggest the extent of the delocalized orbitals. (Details are discussed in chemistry textbooks.)... 

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