Organic Chemistry / Alkane Combustion
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Solution: In each of the following groups of compounds, identify the o...

Question

In each of the following groups of compounds, identify the one with the largest heat of combustion and the one with the smallest. (Try to do this problem without consulting Table 2.3.)

(d) Pentane, 3-methylpentane, 3,3-dimethylpentane

Video Transcript

Hey everyone, let's compare our three molecules, we have pentane 3-methyl pentane and 3,3 dimethyl pentane, okay? So when looking at these, we can draw all of them out, pentane we know this is going to be five carbons, here we have another pentane. So, another five carbons, so at position 3, we're going to have a CH3 group, for the last one we're going to have another pentane molecule except now position 3 we have 2 methyl groups. So, CH3 and CH3. Now, what we can do is we can look at our rules that we know. so here we can say we're comparing one molecule that has five carbons, one that has six, one that has seven, so we know that as we increase the number of our carbons we're also going to increase our heat of combustion, so we're going to say that our molecules all the way to the right it's going to have the highest heat of combustion and the molecule all the way to the left, we're going to have the lower here of combustion, okay? So that's it for this a problem, let me know if you have any questions.