[Jeebus]

Howdy,

I am just revising and two of the questions I've come across are causing me problems, I have the solutions posted a little bit further down, I just have NO idea how I would go about doing them myself :

"Draw the structure of any one of the isomers of the third member of the alkene series. Indicate clearly which carbon atoms have planar bonding and which are bonded tetrahedrally."

How do you know what the third member of the alkene series is, and how do you draw it ? If someone can explain or link me to a website that will explain I would really appreciate it ! Thanks a lot.

I know if theres a double or triple bond then its planar and if there none then its tetrahedral, yeah ? Thanks!




The other question is :

"The ionic addition mechanism for the reaction of ethene with bromine water involves the formation of an intermediate ionic species. Draw the structure of this species.

Give the names or structural formulas of the three products that would be formed if the bromine water used in the reaction contained sodium chloride.\

How does the formation of these three products support the mechanism of ionic addition?"

I really don't understand how you would come to the answer of any of these questions. The answers are here :

http://www.examinations.ie/archive/markingschemes/2008/LC022ALP000EV.pdf

Question 9, (b) and (d).

The question in its entirity is here :

http://www.examinations.ie/archive/exampapers/2008/LC022ALP000EV.pdf

Thanks so much for the help !

[Astrokel]

helllo.

"Draw the structure of any one of the isomers of the third member of the alkene series.

ethene,propene,butene,.

I know if theres a double or triple bond then its planar and if there none then its tetrahedral,

yes you need to determine the hybridisation of the carbon atoms.

How does the formation of these three products support the mechanism of ionic addition?"

First bromine will undergo heteolytic fission and the Br⁺ electrophile will attack the ethene, forming a bromonium ion(the cyclo with a + localised on bromine) and this intermediate is a positive. If without sodium chloride, you have OH-, H2O and Br- nucleophiles to attack on the brominium ion intermediate to yield, halogeno-alcohol and halogenoalkane. Did you notice the characteristics of the 3 nucleophiles?, they are negative. The addition of sodium chloride contains a negative specie of Cl- which also could attack the intermediate positive ion to yield the final product of halogenoalkane containing bromine and chloride. This certainly proved the ionic addition of mechanism, because it confirms the intermediate is positive since it could 'finish off' by negative anion.