Carbon hydrogen bending alkanes

B. Carbon-hydrogen bending vibrations of branched alkanes... 

Although non-cyclic alkanes are called straight-chain alkanes they are technically made of kinked chains. This is reflected in the line-drawing method. Each ending point and bend in the line represents one carbon atom and each short line represents one single carbon-carbon bond. Every carbon is assumed to be surrounded with a maximum number of hydrogen atoms unless shown otherwise. 

Figure 4.3 Principal modes of vibration between carbon and hydrogen in an alkane (a) symmetrical stretching, (b) asymmetrical stretching and the bending vibrations, (c) scissoring,...

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