# Homework Help: Which has higher polarity, sec-butyl chloride or tert-butyl chloride?

1. Jul 17, 2007

### FlipStyle1308

1. The problem statement, all variables and given/known data
I just need to know which of the two, sec-butyl chloride or tert-butyl chloride, has the higher polarity.

2. Relevant equations
I know that better electron withdrawing groups have higher polarity.

3. The attempt at a solution
I am learning towards sec-butyl having a higher polarity due to since it is a secondary carbon, but I would like a confirmation on whether my answer is correct or not. Thanks.

2. Jul 18, 2007

### chaoseverlasting

Yes. That would be true. The greater the s character, the higher the polarity.

3. Jul 18, 2007

### chemisttree

Without measuring this it is difficult to say. Polarity is also a function of charge separation. T-butyl is a better electron donor than sec-butyl. This could result in a higher negative charge on the chlorine and a higher postive charge on the teritiary carbon of the t-butyl group. This charge separation could cause the t-butylchloride to be of higher polarity.

The permittivity for sec-butyl chloride is 8.564 and that of t-butyl chloride (2-chloro-2-methylpropane) is 9.663. (CRC Handbook of Chemistry and Physics, 84th ed., Chap. 6, p 161.) That of 1-chlorobutane is 7.276. It seems to follow the carbocation-stabilizing ability of the carbon attached to the chlorine. The permittivity for 1-chloro-2-methylpropane, another form of butane that has a primary chloro group, is 7.027. This is somewhat lower than 1-chlorobutane (7.276) which indicates that the permitivitty is not solely determined by the nature (primary, secondary, tertiary...) of the chlorine substitution.

4. Jul 20, 2007

### FlipStyle1308

Great, thank you for confirming my answer!

5. Jul 20, 2007

### chemisttree

6. Jul 20, 2007

### FlipStyle1308

Confirming the answer I suspected in the original post. I was leaning towards sec-butyl, and you guys agreed.

7. Jul 22, 2007

### chemisttree

What parameter do you think is used to measure polarity?

8. Jul 23, 2007

### Gokul43201

Staff Emeritus
On the contrary, c-tree has shown that tert-butyl chloride has a greater polarity. The inductive effect of 3 independent methyl groups is greater than that of 1 methyl and 1 ethyl group. The inductive effect from an n-carbon alkyl group does not increase as rapidly as n. But, as mentioned above, there are also effective separations to keep in mind, which makes the determination more complex. I'm guessing it's the smaller charge separation that gives 1-chloro-2-methylpropane a smaller dipole moment than 1-chlorobutane.

Last edited: Jul 23, 2007