Converting Skeletal Structures to Condensed Formulas, and Vice Versa

Skeletal Structures - Rules In order to understand to convert skeletal structures to condensed formulas and vice versa, you need to understand those rules discussed in “Drawing Skeletal (ZigZag) Structures” or else none of it makes any sense so make sure you have those rules nailed down first!

Perhaps you need a middle man? This can be a hard transition – going from all letters to all lines (or the other way around). You may want to consider drawing the Line- Bond Structures as intermediates, until you are fully comfortable.

Make that transition Take the following condensed formula and convert it to a Line-Bond Structure: (CH 3 ) 2 CHCH 2 CH 3

Making the transition… Adding in all of those lines gets you to: Now get rid of the letters… Off with those H’s and C’s!

Made the transition!

Can turn that process around… Put back the letters and lines to make a Line- Bond Structure for this:

Transitioning again… Adding in the letters… Then taking out the lines…

Transitioning again… Now take out the rest of those lines…

Finish it off… Now remove those C-C lines: Use those parentheses! You can probably even condense that C=C: CH 3 CH 2 CH(OH)CH 2 CHCH 2

You don’t HAVE to draw Line-Bond Structures… Once you get comfortable with skeletal structures, you can go straight to condensed formulas. The end of lines are CH 3, at the intersection of two lines is a CH 2, at that of three lines is CH and at that of four lines is a C… Consider:

Evaluate your intersections Based on ends and intersections, the condensed formula should be: CH 3 CH 2 CH 2 CH 2 CH 3

Try that again… Consider how many ends and intersections are involved: You have branches this time. Watch your parentheses!

Evaluate and Condense Three single carbon ends on the left all attached to the same carbon. Intersections of 4 (C), 2 (CH 2 ), 3 (CH) (with a Cl) lines And one end carbon on the right: (CH 3 ) 3 CCH 2 CH(Cl)CH 3

Try that yet again… Consider how many ends and intersections are involved: You have branches again. Watch your parentheses!

Evaluate and Condense This one is interesting… There’s an OH on an end and a CH 3 branch (facing south) and a 2 carbon branch (CH 2 CH 3 ) facing north… Notice though that the right side is ALSO a 2 carbon group (CH 2 CH 3 )… Can you see it?

Evaluate and Condense So C1 is a two line intersection, C2 is a three line intersection, as is C3. Now track this one, from left to right: HOCH 2 CH(CH 3 )CH(CH 2 CH 3 ) 2

Now, from the other direction How do you turn a condensed formula into a skeletal structure? Do you just start zig- zagging? Usually it helps to identify the backbone of the condensed formula, so you know how many zig-zags to start with and then Numbering the atoms to help correlate them helps, a lot…

Skeletal Structure from Condensed Consider this example, keeping it simple to start: CH 3 CH 2 CH 2 CH 3 Find the basic carbon chain (kind of obvious on this one, I hope). Highlighting those carbons, or numbering them helps keep track of what is where. CH 3 CH 2 CH 2 CH 3

Skeletal Structure from Condensed There are four carbons in the back bone: CH 3 CH 2 CH 2 CH 3 So you need four carbons in a zig-zag: Conveniently, you have nothing else to add!

Skeletal Structure from Condensed Let’s step it up now… Adding parentheses… (CH 3 ) 2 CHCH 2 CH(Br)CH 2 CH 2 CH 3 What is the skeletal structure? Identify the backbone carbons. Stay away from the parenthesis. Once you have found the backbone, you can add the bits and pieces…

Skeletal Structure from Condensed Find each carbon in the main chain, not part of the branches. There are six carbons, outside of the pieces. Draw a six carbon zig-zag… Numbering may help…

Skeletal Structure from Condensed C1 has two CH 3. Add two 1C lines (shown in red). C3 has a Br attached (shown in blue). Answer:

Skeletal Structure from Condensed One more time – draw a skeletal structure CH 3 CH 2 C(CH 3 ) 2 CH(CH 2 CH 3 )CH 2 CH(OH)CH(CH 3 ) 2 Find that back bone…

Skeletal Structure from Condensed Back bone highlighted in red: CH 3 CH 2 C(CH 3 ) 2 CH(CH 2 CH 3 )CH 2 CH(OH)CH(CH 3 ) 2 Seven in the back bone… number left to right… 2 single carbons on #3 (from left side), two-carbon chain on #4, OH on #6 and 2 single carbons on #7.