Alkanes and Alkenes (1 Viewer)

[Kujah]

Okay, we've started this topic and one of the first facts that we've learnt is that alkenes are more reactive than alkanes, and it's got to do with the double bond.

Can someone explain how the double bond would make it more reactive, and what does it mean if the textbook states that the double bond has a "higher electron density"?

Thanks

 

[Mattamz]

because of the double bond, there is four electrons close together, negative charges repel, thus it is more reactive

 

[dan.121212]

This video on youtube explains the reactivity of ethene (an alkene with a double
-C=C-bond) compared to ethane (an alkane with a single -C-C- bond)

since the HSC syllabus focuses on ethene its a great resource - check it out!!!

http://youtube.com/watch?v=4JkfC37oHb4

 

[nandayo]

We're learning this now too.

It's got to do with electron density, but the double bonds aren't of equal strength. One is a sigma bond (the strong one) and one is a pi bond which is kind of bent above it, and weaker.

Because of this pi bond being easy to break, it can be split and other atoms attatched to it, which is why reactions with alkenes are generally addition reactions (because they can just 'jump on' the broken sigma bond) rather than having to react and form two products.

At least that's how I understoood it.

 

[mzduxx2006]

Okay, we've started this topic and one of the first facts that we've learnt is that alkenes are more reactive than alkanes, and it's got to do with the double bond.

Can someone explain how the double bond would make it more reactive, and what does it mean if the textbook states that the double bond has a "higher electron density"?

Thanks

the double bond ensures that once it is broken, each carbon molecule will have an unpaired electron, which will required another electron in order to form a pair. a single bond is already full therefore no more electrons can be accepted. but once that double bond breaks, more electrons can be accepted untill a full pair is achieved.