polarity in gc

[dmd20000]

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why is c-cl more polar than c-br and c-F?

 

[polarmolar]

where did you find this?

 

[glk2101]

hmm not sure?
i know that as one moves down the column from f to cl to br to i the atom gets larger, and even though electronegativity decreases, there is more room for the electrons to move around, thus making br a much better leaving group than f..

 

[klutzy1987]

why is c-cl more polar than c-br and c-F?

Its not, C-F is the most polar of these bonds. Elcectronegtivity decreases as you move down a group and as you move left across a period. Flourine is higher up than Chlorine and therefore is more electronegative and therefore the electronegativity difference will be greater for Flourine
(4-2.1=1.9) while Chlorine is (3.5-2.1=1.4). Polarity is calculated by electronegativity difference and Flourine will always be the most polar.

 

[dmd20000]

i was reading the powerpoint lecture and the professor asks
.Q: Why is the C-F bond less polar than the C-Cl, since F is .
. more electronegative than Cl? .


c-f is 1.51
c-cl is 1.56
c-br is 1.48

i am confused about this concept.

 

[doc toothache]

http://www.chemguide.co.uk/basicorg/bonding/eneg.html
http://www.chemicool.com/elements/fluorine.html
http://www.800mainstreet.com/5/0005-008-negativity.htm

 

[Doa110]

i was reading the powerpoint lecture and the professor asks
.Q: Why is the C-F bond less polar than the C-Cl, since F is .
.more electronegative than Cl? .


c-f is 1.51
c-cl is 1.56
c-br is 1.48

i am confused about this concept.

C-F bond is the shortest of all the Carbon-halides, thus it's extremely endothermic, the most stable, and the least reactive. For molecules tobe polar, the bond between them must be broken.
In the other hand C-Cl, has longer bond length and Cl is a better leaving group than F. But the point here is to look at the bond length of the molecules. So considering bond length, the polarity in descending order would be:
C-Cl>C-Br>C-F
Hint: Flourocarbons are considered "ozon safe" due to their low reactivity.
Now, if you add chlorine to C-F, it becomes a sereious concern for ozon layer! Also there is something related about halogens reactivity in destroyer.(Question 1-40) Sorry I don't recall the exact # of the question.

 

[unitix]

http://www.chemguide.co.uk/basicorg/bonding/eneg.html
http://www.chemicool.com/elements/fluorine.html
http://www.800mainstreet.com/5/0005-008-negativity.htm

Awesome sources!!! 😀