103 - Practice Problem 1-3 Answer Without reference to a...

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Practice Problem 1-3 Answer Without reference to a table of characteristic IR absorptions, which member of each pair do you expect to occur at the higher frequency? (a) C=O or C=C stretching Oxygen is smaller than carbon, because it is further to the right in the same period (atomic size decreases moving from left to right across a period; this is a periodic trend that you should have learned about in general chemistry). A C=O bond is therefore shorter, and stronger, than a C=C bond. Stronger bonds vibrate at a higher frequency. (b) C C or C=O stretching A triple bond is stronger than a double bond. Stronger bonds vibrate at a higher frequency. (c) C=O or C O stretching A double bond is stronger than a single bond. Stronger bonds vibrate at a higher frequency. (d) C H or C Cl stretching H is significantly lower in mass than Cl. Each is attached to carbon. A lighter atom attached to carbon will undergo a stretching vibration at a higher frequency compared to a heavier atoms attached to carbon (an illustration of the mass effect we discussed in lecture). Practice Problem 1-4
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This note was uploaded on 10/25/2010 for the course CH 310n taught by Professor Iverson during the Summer '08 term at University of Texas at Austin.

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103 - Practice Problem 1-3 Answer Without reference to a...

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