Naming hydroxynitriles

Hey,
I'm really confused...I understand the nucleophillic addition rection between HCN and aldehydes and ketones and i understand that a hyroxynitrile is formed but what i don't understand is how to name them....

I've read in a text book we have to include the C-atom attached to the C-N right and we have to include this c-atom in the longest chain...but i'm confused in actually naming them...

Also is the hyroxyl group the CN or the OH or both..... :confused:

Any help will be appreciated
Thank you
Sabrina

Reply 1

Mist

7

Muggle Born

Hey,
I'm really confused...I understand the nucleophillic addition rection between HCN and aldehydes and ketones and i understand that a hyroxynitrile is formed but what i don't understand is how to name them....

I've read in a text book we have to include the C-atom attached to the C-N right and we have to include this c-atom in the longest chain...but i'm confused in actually naming them...

Also is the hyroxyl group the CN or the OH or both..... :confused:

Any help will be appreciated
Thank you
Sabrina

Ok so...

Remember when this reaction occurs the length of the carbon skeleton increases. So if you react ethanal with HCN you get 2-Hydroxypropanenitrile. why that name? Well longest carbon skeleton is 3 (hence propane), the Alcohol (OH) and Nitrile (C=-N) groups both 'compete' for the ending and by 'law' or w/e the nitrile gets the ending and it gets the prefix hydroxy instead to describe the fact it has an alcohol group. It is always 2-hydroxy... since the chain is named from the functional group end with the nitrile carbon being carbon no. 1. It has the nitrile ending because it is a nitrile... It rely needs a diagram to help explain, that was probably a little confusing

-----O----------------------OH<----------- 2 Hydroxy
CH3-C -H + HCN ----> CH3 - C - C=-N <--- Nitrile
----------------------------H<------------ 3 carbons overall

If you have a ketone, the group you have instead of the H in an aldehyde becomes a branch on the new molecule, so if you react propanone with HCN you get 2-Hydroxy-2-methylpropanenitrile: This
------OH-------
CH3 - C - C =-N
-----CH3-------

If you have a bigger ketone or aldehyde, the longest carbon chain changes, so with butanone you get...
-------OH-------
C2H5 - C -C =-N which is 2-hydroxy-2-methylbutanenitrile
------CH3------

For sumthing even more nasty like the 2-methylbutanone you'd get...
-----CH3-O------------------CH3-OH---------
CH3 - C - C - CH3 ----> CH3 - C - C - C =-N <--- errr 2-Hydroxy-2,3-Dimethylbutanenitrile...(?)
------H-----------------------H--CH3-------
thats like the best I can do on here :frown: