PLEASE help, dimers??

[113zami]

can someone please help me with this question, THANKS

which molecule is likely to form dimers?

a)BF3
b)NO2-
c)NO2
d)NO2+

the correct answer is C , C is a radicle and I can uderstand why it would form dimers but why wouldn't the other choices be able to form dimers?, to my knowledge any 2 molecules can form dimers there isn't really a restriction to forming dimers am i right

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[theedaddy77]

wtf is a dimer?

 

[113zami]

a good example would be when 2 molecules capable of forming hydrogen bonds come near each other such as 2 carboxylic acids, when they come near each other and form hydrogen bonds, that's a dimer,

 

[theedaddy77]

a)BF3
b)NO2-
c)NO2
d)NO2+

For a there is an acid but no base so yeah
for b it is resonace stablized no reaction
for c has a loan pair therefor a reaction is possible which allows for dimar to happen
for d also stable due to resonace.

 

[osimsDDS]

a good example of a dimer is any carboxylic acid....think about their hydroxyl group and the carbonyl group of 2 carboxylic acids, they would H-bond.

It is kinda small but squint and ur good haha:

http://www.chemguide.co.uk/organicprops/acids/dimer.gif