[Araconan]

Hello, I'm currently attempting the following problem:

Question Explanation:

Graphite oxide (GO) is a compound obtained by treating graphite with strong oxidizers. In GO
carbon honeycomb layers are decorated with several types of oxygen containing
functional groups. A net molecular formula of GO is СОXНY, where X и Y depend on the method
of oxidation. In recent years GO has attracted much attention as a promising precursor of
graphene, the most famous two-dimensional carbon nanomaterial with unique electrical
properties. The exfoliation of graphite oxide produces atomically thin graphene oxide sheets.
The reduction of the latter produces graphene.

Question:

1. Give two reasons why GO is more favorable precursor of graphene, compared to graphite
itself? What in your opinion is the most serious disadvantage of GO as a graphene precursor?

2. The simplest model of the GO sheet is the Hoffman model. It was
assumed that only one functional group, namely (–O–) is formed in the carbon plane as a result
of the graphite oxidation. Calculate Х in the net formula СОХ of GO, if 25% of carbon atoms in
GO keep the sp2 hybridization. What is the maximum Х in the Hoffman model?

My attempt:

I'm honestly, clueless. No textbook that I've read (which is primarily Zumdahl's Chemical Principles) have ever covered or explained problems like these. With regards to question one, I would guess that perhaps the OH groups in the graphite oxide makes it easier to dissolve in a polar substance that might be required during exfoliation? (Although I'm not quite sure of the exact process for exfoliation of graphite oxide). Or perhaps the resulting graphene has better conductivity, allowing the resulting carbon nanotubes to be better conductors? Or the OH groups themselves may take part in hydrogen bonding, strengthening the graphite oxide as opposed to pure graphite, which makes the exfoliation process easier?

With regards to question 2, I was basically trying to figure out how many carbons would have sp2 hybridization in graphene, and that number should equal the number of ether groups in the graphite oxide (assuming that the reduction process only produces double bonds). But I had trouble figuring out a equation between the number of carbons, and the number of double bonds.

If someone could offer some insight, advice, and help, that would be much appreciated Also more importantly, I really wish to know both what kind or type of problem this is, as well as which area of Chemistry does it fall under? So that I may do some extra reading and try more problems like these.

Thanks in advance!

[Corribus]

For (1), you are on the right track with solubility.  Exfoliation just means separation of the individual sheets.  You can think of layered solids like graphine as consisting of lots of single layers that are glued together by their mutual attraction to each other.  The trick is to pull them apart but still retain their natural character.  Nobody has figured out a perfect way to do this with graphene yet.  But in theory if you can increase the solubility of individual layers in the external medium, you can make it easy to peel them apart.  Graphene sheets are very nonpolar and the interaction between sheets is very strong, driven in large part by the delocalized pi-electron systems that like to sit on top of each other.  All aromatic systems do this to some extent, and the larger the aromatic, the greater the effect.

I'm not sure why anyone at undergraduate level would come up with an answer for a disadvantage of oxidizing graphene without looking it up, considering that it took a lot of sophisticated experiments to figure out these disadvantages in the first place.  And researchers still don't quite understand why it happens.  I guess by way of a hint, I can offer this: suppose I gave you a stack of pristine dollar bills that were all stuck together with water soluble glue, and I told you that I want you to separate them, but that they're only good to me if they're still pristine looking once you're done.  You might think, "well, if I soak them in water, that will dissolve the glue, and the bills will separate.  Then I can dry them and you have your bills nice and separated."  What might be the problem with this solution? 

As for (2), first it's Hofmann's model, not Hoffman's model.  That might help you search for information on the topic.  On that note, maybe this review will help:

http://bucky-central.me.utexas.edu/RuoffsPDFs/211

Your final question - this would fall under materials science and nanoscience.  Graphene is a very hot topic right now in electronic materials research. 

EDIT: Removed my mini-rant about my dislike of questions like this.  Decided it was not really an appropriate place to mount a soap-box.