63E4159SPartAPages213-220

63E4159SPartAPages213-220 - PRELABORATORY QUESTIONS AND...

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PRELABORATORY QUESTIONS AND SUPPLEMENT TO HOLUM EXPERIMENTS 41 AND 59 The following terms and examples are to be used as a supplement for experiments 41 and 59 in the Chem 1024 Holum laboratory manual. Organic chemists often use structural formulas to represent organic molecules. Two of the various types of structural formulas that are used to represent organic molecules are called full or expanded structural formulas and condensed structural formulas . In a full or expanded structural formula , every atom and bond between each atom is shown. In a condensed structural formula every atom is shown while most if not all of the bonds between the atoms are not shown. Here are some examples of some alkanes that illustrate these concepts. Alkanes consist of carbon and hydrogen atoms that only contain single bonds. CH 4 is called methane . CH 4 is an example of a condensed structural formula. We can convert the CH 4 condensed structural formula into a full or expanded structural formula by placing C at the center of a drawing and then symmetrically arranging the four H atoms around the central C atom as follows: H H C H H The next step involves placing single bonds between the C and H atoms. A single line represents each single bond and a single line represents two electrons. The complete full or expanded structural formula for CH 4 is as follows: H H C H Full or expanded structural formula for methane H The four H atoms in methane, CH 4 , are called equivalent since these four H atoms are all in identical environments . The environment of each hydrogen atom is determined by looking at the atom that the H atom is directly bonded to and then looking at the other atoms that are bonded to the atom that the H atom is directly bonded to. In the case of methane, CH 4 , each H atom is directly bonded to a C atom that is also bonded to three other H atoms. Thus each of the four H atoms in methane, CH 4 , is in identical environments and are said to be equivalent. In our next example CH 3 CH 3 is called ethane . CH 3 CH 3 is an example of a condensed structural formula . 213
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We can convert the CH 3 CH 3 condensed structural formula into a full or expanded structural formula by placing both C atoms at the center of a drawing and then symmetrically arranging the six H atoms around the two central C atoms as follows: H H H C C H H H Each carbon atom is bonded to three H atoms due to the two CH 3 units in CH 3 CH 3 . The next step involves placing single bonds between the two C atoms and the C and H atoms. A single line represents each single bond and a single line represents two electrons. The complete full or expanded structural formula for CH 3 CH 3 is as follows: H H H C C H Full or expanded structural formula for ethane H H The six H atoms in ethane, CH 3 CH 3 , are called equivalent since these six H atoms are all in identical environments. As in the case of methane, determine the environment of each H atom by looking at the atom that the H atom is directly bonded to and then
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63E4159SPartAPages213-220 - PRELABORATORY QUESTIONS AND...

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