You can see that Point F is not on this line, so F is not collinear with C, D, and E. And if you look at Point F here, I drew this in to draw a contrast. So here we could have, C, D, and E are all collinear. You can have points be collinear, that is, they share the same line. Now this arrow here extends infinitely in that direction. And these arrows tell you, the geometry student, that it extends infinitely in this direction. But notice how I'm writing the arrows above my letters I have arrows on either side. Or if you have some sort of smaller letter over here, we can call this Line L. Now when you're labeling a line, it's key to include at least two points. So a line is going to be all the points, and we can actually select two of them to name it. And a line is set of points or, the word that you might learn later is locus, extending in either direction infinitely. So you can think of coplanar as sharing the same plane. So "co", you can think of it as a word for sharing. So two things are coplanar if they are, just like we have in the picture here, in the same plane. You could call this plane, Plane ABC.ĭefinition of coplanar: We actually can define this, is points, lines, or anything, segments, polygons in the same plane. So let's say you had a point right here: Point A, Point B, and Point C. And collinear we'll talk about in a second here, but collinear means they're not on the same line. Now you can name a plane using a single capital letter, usually written in cursive, or by three non-collinear points. Secondly, this paper actually has some thickness and a plane will not. Or if there are two differences between a sheet of paper and a plane, the first is this paper does not extend in every direction. So one way to visualize what a plane could be is to think about a sheet of paper. A plane is a flat surface that has no thickness, and it will extend infinitely in every direction. And the way that we label it is with a capital letter. A point has no size it only has a location. Now we're not really defining point, we're just describing it. So let's go back and define these as much as we can. And the third undefined term is the line. From these terms we define everything else. The two molecules above are different, prove this to yourself by building a model.There are three undefined terms in geometry. Below are two drawings of a 4-carbon molecule with two chlorines and two bromines attached.Ĥ-carbon molecule with 2 chlorines and 2 bromines 4-carbon molecule with 2 chlorines and 2 brominesīoth drawings look like they represent the same molecule however, if we add dashes and wedged we will see that two different molecules could be depicted: This drawing method is essential because the placement of different atoms could yield different molecules even if the molecular formulas were exactly the same. The majority of the drawing is Bond-line (zig-zag) formula, but the -CH 3 are written as condensed formulas, and the -OH group is written in Kekul é form.Ī widely used way of showing the 3D structure of molecules is the use of dashes, wedges, and straight lines. It will be more helpful if you become comfortable going from one style of drawing to another, and look at drawings and understanding what they mean, than knowing which kind of drawing is named what.Īn example of a drawing that incorporates all three ways to draw organic molecules would be the following additional drawing of Retinol. The different ways to draw organic molecules include Keku l é (straight-line), Condensed Formul as, and Bond-Line Formulas (zig-zag). Through general chemistry, you may have already experienced looking at molecular structure. Another good idea is to get a model kit and physically make the molecules that you have trouble picturing in your head.
At first it may seem difficult or overwhelming, but the more you practice looking at and drawing organic molecules, the more familiar you will become with the structures and formulas.
Some people say that Organic Chemistry is like another language, and in some aspects, it is. Learning and practicing the basics of Organic Chemistry will help you immensely in the long run as you learn new concepts and reactions.
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