Using organic chemistry I have failed to find a method that doesn't involve halogens (gasseous especially).

Please ignore the enzyme mono-oxygenase, which adds $\ce{O2}$ directly to alkanes to form alcohols.

[edit] Regarding selectivity the reaction should preferably stop at the alcohol stage.

The most promising method I have found involves Boranes, but only works for terminal alkanes. The termial organoborane can then be converted to an alcohol.

I found it using a google search inspired by the answers below: "photochemistry of alkanes."

  • $\begingroup$ A haloalkane is not really an alkane. What starting materials can you use? It is not clear from the question. $\endgroup$
    – Jori
    Mar 14 '15 at 16:30
  • 3
    $\begingroup$ Conversion between alkane and alcohol can be done in various ways. Btw I don't think this q. is unclear. $\endgroup$
    – Mithoron
    Mar 14 '15 at 16:58

I think that you're asking if there is a way to convert an alkane to an alcohol without using halogens in the process.

Alkanes are relatively unreactive and so high energy species (like free radicals) are most often used to carry out reactions on alkanes. The reaction of alkanes with halogens that you've mentioned is an example of this free radical process.

Other high energy molecules that can be used to convert alkanes to alcohols include ozone and (photo-) chemically generated singlet oxygen. Just like with the halogens, these reactive molecules show little selectivity, so if primary, secondary and tertiary hydrogens co-exist in your alkane, then a mixture of primary, secondary and tertiary alcohols result. However in molecules such as cyclohexane, where there is only one type of hydrogen, somewhat useful results can be obtained. I say "somewhat useful" because ozone and singlet oxygen can oxidize the resultant alcohol further to a carbonyl. Here is a reference to an abstract on the use of ozone to functionalize alkanes.

Reagents such as potassium permanganate and chromic acid also oxidize alkanes by a free radical mechanism to produce alcohols. Again the issues of selectivity and further oxidation remain.

Here is a link to a nice review entitled "Alkane Hydroxylation." It covers a wide variety of reagents. Most of the molecules depicted contain functional groups which can help improve selectivity, but there are a number of hydrocarbon examples as well. Perhaps you'll find an example that is similar to your molecule of interest.

  • $\begingroup$ Nice answer. You definitely have stronger oxidants than Kalus! I chose Klaus' answer because his method is more specific in that it is capable of stopping at the alcohol stage. $\endgroup$
    – Dale
    Mar 14 '15 at 18:11
  • $\begingroup$ @JoeHobbit I don't think so. Wikipedia says, "The free radicals generated by this process then engage in secondary reactions. For example, the hydroxyl is a powerful, non-selective oxidant. Oxidation of an organic compound by Fenton's reagent is rapid and exothermic and results in the oxidation of contaminants to primarily carbon dioxide and water." $\endgroup$
    – ron
    Mar 14 '15 at 18:22
  • $\begingroup$ Maybe if a protecting group were added to the solution that would latch onto the alcohols produced before further degradation. $\endgroup$
    – Dale
    Mar 14 '15 at 18:46
  • $\begingroup$ That's a possibility, something that reacts rapidly with alcohols (TosCl?). Have you had a chance to look through the "Alkane Hydroxylation" link I added? I was surprised by how selective some of the pure hydrocarbon reactions were, and that conditions could be tuned to optimize alcohol yield. $\endgroup$
    – ron
    Mar 14 '15 at 18:52
  • $\begingroup$ The use of Platinum Chlorides to make termial alcohols is great! $\endgroup$
    – Dale
    Mar 14 '15 at 19:01

ron has already pointed out that the functionalization of alkanes often involves radicals.

A classical process is the Fenton reaction, typically using $\ce{FeSO4}$ and $\ce{H2O2}$.

Here, the reactive species is the hydroxyl radical, $\color{\red}{\ce{HO\cdot}}$, which is generated via:

\[\ce{Fe^{2+} + H2O2 -> Fe^{3+} + OH- + \color{\red}{HO\cdot}}\]

In a variant, the photo-Fenton reaction, the process is facilitated by UV/VIS irradiation.

Irradiation in the visible range enables photoreduction of $\ce{Fe^{3+}}$ to $\ce{Fe^{2+}}$, furnishing more hydroxyl radicals:

\[\ce{Fe^{3+} + H2O ->[h\nu] Fe^{2+} + \color{\red}{HO\cdot} + H+}\]

Upon irradiation at wavelength below 400 nm, direct excitation (and homolytical cleavage) of hydrogen peroxide provides an additional source for the reactive species:

\[\ce{H2O2 ->[h\nu] 2\color{\red}{HO\cdot}}\]

However, due to the lack of selectivity, this process is rarely used in synthesis and rather applied for the opposite: degradation of organic matter in wastewater treatment.

  • $\begingroup$ Precisely what I was looking for! Would the photo-Fento reaction would be at all hindered by a moderately alkaline environment? pH=9 $\endgroup$
    – Dale
    Mar 14 '15 at 18:15
  • $\begingroup$ Admittedly, I've never seen Fenton ot photo-Fenton reactions under alkaline conditions. The solution of iron(II)sulfate itself is quite acidic, btw. And again, this isn't a really useful method other than for the degradation of organic matter, such as in waste water treatment (reduction of TOC and degradation of chlorophenol in paper industry). $\endgroup$ Mar 14 '15 at 18:19
  • $\begingroup$ I wonder if a dilute solution could achieve a reasonable yeild of alcohol. $\endgroup$
    – Dale
    Mar 14 '15 at 18:44

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