VISUAL SKILLS Visualize the structural formula of each of...

VISUAL SKILLS Visualize the structural formula of each of the following hydrocarbons. Which hydrocarbon has a double bond in its carbon skeleton? $$\begin{array}{ll}{\text { (A) } \mathrm{C}_{3} \mathrm{H}_{8}} & {\text { (C) } \mathrm{C}_{2} \mathrm{H}_{4}} \\ {\text { (B) } \mathrm{C}_{2} \mathrm{H}_{6}} & {\text { (D) } \mathrm{C}_{2} \mathrm{H}_{2}}\end{array}$$

VISUAL SKILLS Visualize the structural formula of each of
the following hydrocarbons. Which hydrocarbon has a double
bond in its carbon skeleton? $$\begin{array}{ll}{\text { (A) } \mathrm{C}_{3} \mathrm{H}_{8}} & {\text { (C) } \mathrm{C}_{2} \mathrm{H}_{4}} \\ {\text { (B) } \mathrm{C}_{2} \mathrm{H}_{6}} & {\text { (D) } \mathrm{C}_{2} \mathrm{H}_{2}}\end{array}$$

Key Concepts

Double Bonds

A double bond involves the sharing of two pairs of electrons between two atoms, often represented by two parallel lines in structural formulas. The presence of a double bond in a hydrocarbon indicates unsaturation, meaning that the molecule has fewer hydrogen atoms than a saturated analogue, which significantly affects its chemical behavior and reactivity.

Hydrocarbon Classification

Hydrocarbons are organic compounds composed exclusively of carbon and hydrogen. They are classified based on the types of bonds present between carbon atoms—typically into alkanes (only single bonds), alkenes (at least one double bond), and alkynes (at least one triple bond). This classification is fundamental in determining physical properties and reactivity.

Structural Formulas

Structural formulas are visual representations of molecules that illustrate the arrangement of atoms and the chemical bonds between them. They are crucial for understanding the connectivity and geometry of a molecule, which aids in predicting chemical behavior and reactivity.

Transcript

00:01 So this comes from chapter 4, problem 4.

00:03 It's asking you to visualize the structural formula of each of the following hydrocarbons and determine which hydrocarbon has a double bond in its carbon skeleton.

00:11 Now, the easiest way for most of us to visualize something is to draw it out.

00:16 Sometimes if you're confused, the first step to understanding something is to draw it out.

00:21 And then once you draw it out, you realize it's a lot easier than it can be.

00:24 So let's go ahead and draw out each of these hydrocarbons.

00:28 So our first one is c3h8.

00:31 So c3h8.

00:39 I like to start by just drawing out the carbons.

00:43 So let's draw three carbons and make sure that we can connect them to one another.

00:48 We know that they're all going to be bound to each other because carbons are what you use to form chains in the molecules.

00:58 If it's simple hydrocarbons because hydrogens only have one bonding arm.

01:02 And the carbons each have four bonding arms.

01:07 So let's show them bound to one another.

01:12 And now let's see if we can use up all of our hydrogen.

01:16 So remember, carbons need to have their four bonding arms filled, and hydrogens need to have their single one filled.

01:23 So for this carbon, we can put an h.

01:29 Let's put one more h.

01:31 And then let's leave the third bonding arm free now because we don't know if we're going to have another hydrogen here or another double bond.

01:47 So let's just go to the next one and again just the minimal amount of hydrogens.

01:59 And so now we've used up one, two, three, four, five hydrogens.

02:04 So we're able to fit three more.

02:06 So all of these bonding arms of these carbons can be filled.

02:12 With hydrogens.

02:17 Now we can double check.

02:19 So this carbon each has four bonds.

02:24 All of the hydrogens are bound to carbons.

02:27 This carbons got its four arms filled, and this carbon also has its four arms filled.

02:33 So there's no double bonds in this one...

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