Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: toadesque on December 03, 2009, 02:29:12 AM

Title: Did a lab involving some alkyl halides, confused on some questions
Post by: toadesque on December 03, 2009, 02:29:12 AM

Ok so I mixed some NaI-in-acetone solution with a bunch of alkyl halides. One of them was 2-chlorobutane and the other was 2-bromobutane.

The 2-chlorobutane had no reaction after shaking the mixture for 5 minutes and the 2-bromobutane turned partially cloudy.

So now I have to explain why those reactivities were observed. And I have to explain it in terms of their structure (primary, secondary, tertiary, cyclic).

So um, 2-chlorobutane is secondary right? What does that tell me about why there was no reaction?

Title: Re: Did a lab involving some alkyl halides, confused on some questions
Post by: azmanam on December 03, 2009, 07:19:04 AM

you have to look at what's different between the two systems and assess the strengths and weaknesses of those differences and how that changes the rate of the reaction (do you know what kind of reaction you're getting?  SN1/SN2/E1/E2?).  Possible differences: nucleophile, nature of electrophile (methyl/primary/secondary/tertiary/beta-branched..), solvent, and leaving group.

System 1: 2-chlorobutane, NaI, acetone
System 2: 2-bromobutane, NaI, acetone

Title: Re: Did a lab involving some alkyl halides, confused on some questions
Post by: alchmist on December 04, 2009, 12:36:37 AM

the 2-chlorobutane and the 2-bromobutane are different in the respect that the bromine will react faster and is the better leaving group. NaI is soluble in acetone (to a degree) but NaCL is NOT. This is why it gets cloudy and you should observe a precipitate.

You wouldn't happen to go to WCSU would you?