Drawing Alkanes When Given the Structure Name

Drawing Alkanes When Given the Structure Name


In part one, we covered how to name
alkanes when given the structure. So if you missed that you can find that video
here. Now we’ll go over how to draw the structure when given the name. Here’s the
format of each example name we will go over.
Notice how in each example we always have a number in front of our
substituent followed by the longest carbon chain. That number tells us which
carbon that specific substituent is located at. We’ll always start with
drawing the longest carbon chain first then placing the substituents at the
correct locations. Let’s do three different examples that
increase in difficulty. Here’s example 1 step 1 draw the longest carbon chain. I
have a trick on how to draw the correct carbon chain each time count to 1 less
than the number of carbons you want, say we wanted to draw only 8 carbons if we
counted to 8 when drawing so 1, 2, 3, 4, 5, 6, 7, 8 that actually gives you nine carbons
but if we count to 7. 1, 2, 3, 4, 5, 6, 7 that gives us 8 carbons which is what we
wanted so we will do the same for this example since it states octane and we
know that’s 8 carbons. Step two number the carbon chain we can number the carbon
chain either from left to right or right to left, I’ll number it from left to right.
Step 3 place substituents at their designated numbers. In this case we only
have one substituent located at the 4th carbon on our carbon chain
remember propyl has 3 carbons so this is the structure for 4-propyloctane. Here’s
example 2 step 1 draw the longest carbon chain our longest carbon chain is
pentane, pent meaning 5 let’s draw 5 carbons. Remembering the trick where we
count to 1 less than the number of carbons we want so 1, 2, 3, 4 and we
actually drew one, two, three, four, five carbons. Step two number the carbon chain
I’ll number the carbon chain from left to right but you could
have numbered it from right to left. Step 3 place substituents at their designated
numbers, we have two different substituents in this case an ethyl group
and a methyl group, both groups are located at the third carbon this is one
way we could have drawn the structure. We could have also drawn the major carbon
chain going up first and placed the same substituents either way both examples
have the substituents at carbon three so they both are correct. Now for our
more challenging example, example 3 step 1
draw the longest carbon chain our longest carbon chain is butane, but
meaning 4 so we’ll draw 4 carbons so 1, 2, 3 and we drew one two three four carbons.
Step two number the carbon chain I’ll number the carbon chain from left
to right. Step 3 place substituents at their designated numbers whenever we
have a number then a comma followed by another number this tells us that
there’s more than one of the same substituent. In this case we have four
numbers plus the prefix of tetra and tetra means four so we must have four
methyl groups since this is tetramethyl. Our numbers in front tell us we have two
methyl groups on carbon 2 and two methyl groups on carbon 3 and this is the
proper structure. Now if you would like help on your homework, online tutoring or
other helpful resources I have all of that and more in the description box and
remember stay determined you can do this!

9 thoughts on “Drawing Alkanes When Given the Structure Name

  1. One advice to you mam :- You use lots of paper cuts out for you videos if you simply add
    "Text over the Video" by editing it would save your time for making videos.

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