Draw a structure for each alkane. a. 2,2 -dimethylpentane b. 3 -isopropylhept

Draw a structure for each alkane. a. 2,2 ...

Key Concepts

Alkanes

Alkanes are saturated hydrocarbons characterized by only single bonds between carbon atoms. Their general formula is CnH2n+2, and they form the basis for understanding more complex organic structures. Recognizing alkanes is essential when dealing with organic nomenclature and structure drawing.

IUPAC Nomenclature

IUPAC nomenclature is the standardized system for naming organic compounds. It involves identifying the longest continuous carbon chain, numbering it to assign the lowest possible numbers to substituents, and naming all branches as alkyl groups. This system ensures that each compound has a unique and systematic name.

Structural Formulas

Structural formulas depict the arrangement of atoms and the bonds between them within a molecule. For alkanes, this involves drawing the carbon backbone and showing how substituent groups, like methyl, ethyl, or isopropyl, are attached. Structural formulas help visualize molecular geometry and connectivity.

Carbon Chain Numbering and Branching

Numbering the carbon chain correctly is crucial in identifying the positions of branching substituents. This concept ensures that the substituents are given the lowest possible numbers according to IUPAC rules, which minimizes ambiguity in the structure. Understanding the position and identity of branches is key to accurately drawing and naming an alkane.

Transcript

00:03 So in the past, we've used structures and tried to determine the name of a molecule.

00:09 Now let's do the exact opposite.

00:11 Let's use the name and try to develop a structure for these following alkanes.

00:17 So first, let's use three -ethylhexane.

00:22 Three -ethylhexane.

00:23 So let's start off by drawing our hexane, which is six carbons.

00:28 Ch3, ch2, ch2, ch2, ch2, ch2, ch2, ch3.

00:37 That is 1, 2, 3, 4, 5, 6 carbons.

00:41 We have a hexane.

00:42 Now on carbon 3, we want ethyl.

00:45 Now this is where there is a little bit of freedom.

00:47 We can do it on this carbon and make that carbon 3, or we can do it on this carbon and make this carbon 3.

00:56 I like to go left to right.

00:59 It's just easier, and that's how we read books and molecules anyways.

01:04 So let's just go left to right.

01:07 We'll have to get rid of one of these hydrogens so that this bond can be formed.

01:13 So now we'll add our ethel group, ch2, ch3.

01:22 Let's try this example.

01:24 Three -ethyl -3 -methyl pentane.

01:26 We'll start with our parent chain, ch3, ch2, ch2, ch2, ch3.

01:37 And on the third carbon, the middle carbon, there is going to be three ethyl and three methyl.

01:46 Or rather, there's going to be an ethyl group and a methyl group.

01:50 Now, this also means that there are two groups attached to that one carbon, meaning there are two additional bonds that we need.

02:01 So we're going to be deleting both of these hydrogens.

02:05 Both of these hydrants are not going to be part of the molecule.

02:08 Instead, we'll have a methyl group and a nethyl group.

02:15 Now, orientation for this does not matter in this case.

02:19 We don't know stereochemistry, and therefore there's nothing we can do about that.

02:24 However, if you want to make our ethel group up top where the methyl group is and make the methyl group on the bottom, that is totally fine.

02:33 Personal preference.

02:34 I just didn't think i had enough space for an ethel group...

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