Draw the condensed structural formula for each of the following:
a. cis-1,2-difluoroethene

Question

Draw the condensed structural formula for each of the following:

a. cis-1,2-difluoroethene

Accepted Answer

Hi, welcome back everyone. Our next question says, draw the correct structure for sis 34 di bromo, three hexen. And I have four different answer choices labeled a through D with four different possible structures. So we'll look at those in more detail after we figure out what our structure should be to figure out which one matches the one we've arrived at. So we start drawing a structure by looking at that longest carbon chain in our name. So we have hexen, six carbons with a double bond, it's three hexen. So we know our double bond must go from the third carbon. So C three double bonded to C four. So with that in mind, the straw six carbon chain, we're drawing a skeletal structure. It's often easiest to start that way. And we're given skeletal structures. So we have 123456, we'll number them to make sure I've put the correct number of carbons in and to help me draw my structure. So I indeed have six carbons, the double bond from carbon three to carbon four, put that in. And then we're told we have 34 di bromo. So we have a bromine on carbon three and carbon four going to erase my number three and four just to make my bromine fit a little better. So, down from carbon three, I have a bromine and up from carbon four, I have a bromine. The last thing I have to account for is that this is the cis isomer. When I look at what I've drawn, my identical bromine atoms are on opposite sides of the double bond, one going down and one going up. So this is the trans isomer that I've drawn. So in order to draw the cis isomer, I need those brom means to be on the same side of the double bond. So to do that, it's often easiest to start by drawing the double bond first. So I have a double bond here thats between carbons three and four is a bromine on each of those. So I'll draw my first bromine on carbon three going down. And that means carbon four, I need to draw the other bromine also going down. Now, the rest of the molecules essentially two ethyl groups, one on either side. So I draw the first ethyl group. So from carbon three to carbon two, there's one bond and then from carbon two to carbon one and then on the other side, carbon four to carbon five and then to carbon six. So I've got the structure where I have a double bond with two ethyl groups coming up So on the top of the double bond and two bromine groups coming down and that masses my structure for choice B, which looks exactly like that. When I look at my other answer, choices to rule them out. In choice A, the two B Romines are both attached to the same carbon. So this is not correct. When I talk about cyst trans arrangements, I'm talking about the similar substituent being on the two different carbons of the double bond. So that's why choice A isn't correct. In choice C I have the two bromine's on opposite sides of the double bond, one going down and one going up. So this is the trans isomer. So that's why choice C isn't correct. And a little note when you draw that sort of zigzag skeletal structure to start with, you will kind of naturally end up with a trans arrangement if your two substituents are similar, since you tend to draw them alternating up and down. And then finally, in choice D, choice D shows a molecule with two double bonds. So this is not correct. Our molecule should have only one double bond. We would see a second number in front of the vaccine if there were two. So choice D is incorrect. So once again, the correct structure for CIS 34 di bromo three hexen is choice B with the two BROM means on the same side of carbons three and four, see you in the next video.

Draw the condensed structural formula for each of the following:
a. cis-1,2-difluoroethene

Verified video answer for a similar problem:

Key Concepts

Condensed Structural Formula

Cis-Trans Isomerism

Fluoroalkenes