17 February 2011

Alexandra Grove: Bomb Factory Or Drug Factory?

Whilst reading transcripts from the 7th July bomb inquests (Coroner's Inquests into the London Bombings of 7 July 2005 Hearing transcripts – 1 February 2011 - Afternoon session) with a view to understanding the chemical nature of the bombs that were used, apart from hydrogen peroxide, the name of one other chemical kept cropping up again and again: piperine.

Clifford Todd explains (p44 line2),
"1 Our first analysis on some materials from
2 Alexandra Grove showed us the presence of a material
3 called piperine. It later transpires that that is
4 simply something that is contained within black pepper."
I looked up the structure of piperine ...
... and immediately thought of MDMA/ecstacy.

To see why, you need to be familiar with the structure of ecstacy, and see how it compares with piperine. In the diagram, the lower structure is ecstacy (MDMA)
we are already familiar with piperine.

A bit of googling quickly takes us to the drug site Erowid (very useful site for the study of chemistry, btw), which has a couple of pages dedicated to converting pepper to piperonal.

Piperonal, as is obvious from the wikipedia link, is a starting material for the synthesis of ecstacy.

This is depicted in the diagram below; the piperonal to MDMA transformation is seen
in the chemistry section of the MDMA link.

Further thoughts on hydrogen peroxide/piperine as an explosive mixture

Throughout the Hearing Transcripts (I've only made a close study of Coroner's Inquests into the London Bombings of 7 July 2005 Hearing transcripts – 1 February 2011 - Afternoon session) the purity of the piperine isn't made clear. Nor is it made clear why piperine is particularly effective, when mixed with hydrogen peroxide, as a bomb. The idea of a hydrogen peroxide and piperine bomb is something called a Sprengel explosive.

Quoting from wikipedia,
"Sprengel explosives are a generic class of materials invented by Hermann Sprengel in the 1870s.[1] They consist of stoichiometric mixtures of strong oxidisers and reactive fuels, mixed just prior to use in order to enhance safety. Either the oxidiser or the fuel, or both, should be a liquid to facilitate mixing, and intimate contact between the materials for a fast reaction rate."
Applying this to the purported hydrogen peroxide/piperine mixture; supposedly hydrogen peroxide is the 'strong oxidiser' and supposedly the piperine is the 'reactive fuel'. As for 'stoichiometric', this means there is the necessary amount of hydrogen peroxide to piperine in order to oxidise the piperine to carbon dioxide, water and nitrogen dioxide.

The balanced equation is
2 C17H19NO3 + 85 H2O2 → 34 CO2 + 104 H2O + 2 NO2
From the balanced equation we can work out the proportions of piperine to hydrogen peroxide
PiperineHydrogen PeroxideNotes
2 x 285.3485 x 34theoretical calculation
570.682890assuming 100 % pure hydrogen peroxide
15assuming 100 % pure hydrogen peroxide
110assuming a 50 % w/w hydrogen peroxide

As far as I'm aware, we don't know the concentration of the hydrogen peroxide used; depending upon the concentration of the hydrogen peroxide, the ratio of piperine to hydrogen peroxide would be 1 g to 10 g. Does this sound like a thick slurry to you? It certainly doesn't to me.

A thicker slurry needs more concentrated hydrogen peroxide with all of the associated lack of credibility. If the slurry is thicker without the necessary hydrogen peroxide present to oxidise it, the chances of finding traces of piperine post explosion increases.

The choice of hydrogen peroxide as an oxidiser in a Sprengel explosive is a poor choice due to reasons discussed elsewhere (difficulty in obtaining the appropriate concentrations, instability, etc); but why choose piperine as the fuel?

There aren't any obvious reasons. It is a fuel but I don't get the impression it is a particularly reactive one.

Thinking about the two competing hypotheses: drug factory or bomb factory; there is insufficient evidence to conclude one way or the other. But the idea that it was a drug factory is a sensible and viable hypothesis.

Lastly, I wonder if anyone has tried to repeat the chemistry? Extration of piperine from pepper followed by oxidation with hydrogen peroxide, with a view, perhaps, to making piperonal?


  1. Lastly, I wonder if anyone has tried to repeat the chemistry?

    Might be worth reading up on information about the now deceased Terry Jupp of the MoD/DSTL, who was said to be engaged in researching hydrogen peroxide/organic fuels.

  2. @Anonymous 12:21

    I was thinking of whether or not anyone had repeated the chemistry with a view to extracting piperine, and seeing whether or not this can be converted to piperonal with hydrogen peroxide.

    If I were to do the above, rest assured that it would be on a millimolar scale.

  3. I'm pretty sure NO2 isn't formed in explosions by the way... It is N2 gas that is formed.

  4. The equation is theoretical; I took it to that oxidation state in order to try and balance it. It would need to be re-written if any empirical data were generated.

  5. Piperine-Mediated Bioavailability

    If you scroll down to the photograph. The colours of the piperine at different stages of purity reminded me of the following exchange at the Inquest:

    15 Q. Were there different types of sludge at the address?
    16 A. Yes, there were two types. One was much darker than the
    17 other. One was a fairly light, sandy, yellow-brown
    18 colour. The other type was a much darker brown colour.
    19 Q. Was there a difference between them, their effects?
    20 A. Yes. The darker brown material, after various tests
    21 done at the laboratory, was found not to be energetic,
    22 so would not work as an explosive. The lighter,
    23 sandy-coloured material, that was shown, in at least one
    24 specific case
    , to be a high explosive.


  6. These are the ratios and concentrations from hydrogen peroxide + chapatti flour mixture:

    # In its liquid form hydrogen peroxide is available to the public at a strength of 18% and usually available for purchase in 1 litre bottles and 4 litre containers. The prosecution established that between 28 April and 5 July, 443 litres (that is, virtually 100 gallons) of 18% hydrogen peroxide, in a total of 284 bottles and containers, were purchased from three shops in north London. The details of the numerous shopping expeditions need no narration, but the history of the purchase of the hydrogen peroxide in such vast quantities itself tells something of the commitment of the purchasers. The most frequent purchaser was Asiedu, but on one occasion Asiedu and Omar, and on another Asiedu and Ibrahim were involved together, and the conversations with the shop owners or assistants included requests for hydrogen peroxide at 60-70%, strength or for the highest available percentage of hydrogen peroxide.

    # The hydrogen peroxide was taken from the shops to Curtis House and boiled in 2 saucepans and a frying pan. The police were later to recover timetables which appeared to set out a rota for Ibrahim, Asiedu and Omar to oversee the boiling process. On the reverse of one document there were handwritten calculations, consistent with being part of the process by which the percentage strength of the concentrated peroxide was calculated. There was also evidence that the strengthened peroxide was mixed with chapatti flour at Curtis House, where an almost empty 2 kg bag of flour was found, together with residue from the main charge in the living room. Pieces of paper in Ibrahim's handwriting which included notes about an experiment which would enable the concentration of a substance to be determined by metric analysis were also found.

    # 228 bottles were recovered from Curtis House, of which 36 had hand-written markings on them with the figure "70" or "70%". This was the essential ingredient, and if the hydrogen peroxide had reached the level of concentration shown on the written markings on the bottles, the bombs would have exploded as intended. These hand-written markings on the 36 bottles provided compelling evidence that the manufacturers of the bomb believed that this critical strength had been achieved. Later scientific analysis showed that the actual hydrogen peroxide strength found in the bombs was 58% or a little stronger, mixed in a ratio of about 70:30 with chapatti flour. This is the ideal ratio of peroxide to flour for the purpose of causing an explosion, but scientific testing showed that with an ingredient of 58% hydrogen peroxide strength, the mixture would fail to explode. When tests were carried out with peroxide in the mixture in the region of 70% the main charge exploded every time.

    # If these were hoax bombs we find it hard to conceive why it was necessary for the peroxide to be boiled in order to increase its concentration, or why both Asiedu and Yahya, independently, when buying hydrogen peroxide asked for it to be supplied at 60-70% strength, or the highest available percentage. Equally, it is astonishing to imagine why nearly 100 gallons of hydrogen peroxide was needed unless its purpose was to increase its strength. The handwritten figures "70" or "70%" of 36 bottles made devastating evidence.


    Would those ratios lead to a 'thick slurry'?

    Plus, wouldn't they have mixed the Hydrogen Peroxide with the black pepper, rather than extracting the piperine and then mixing it with the HP? How would this change your analysis?

  7. ^ Hi Anonymous - there isn't enough information to draw a sensible conclusion. Thanks for the link, though.

  8. Thanks for the reply. What reason though did you have for deleting the other comment, which was about the composition of the explosives?

    There was nothing that wasn't already in the public domain via Sky News or the BBC.

  9. "What reason though did you have for deleting the other comment"

    It ended up in my spam trap ... subsequently retrieved and posted.

    "Thanks for the reply" ... what I would like is to do some experimental work and report it on this blog. As yet, I haven't had the opportunity to do this work.

    @Anonymous 10.42 "Would those ratios lead to a 'thick slurry'?"

    Without doing the empirical work, I wouldn't know.

    "Plus, wouldn't they have mixed the Hydrogen Peroxide with the black pepper, rather than extracting the piperine and then mixing it with the HP? How would this change your analysis? "

    These questions could all be answered by doing experimental work. Frustratingly, this is at an undergraduate level of skills.

    I would want to (i) isolate, purify and characterise piperine and its isomers; (ii) determine whether or not hydrogen peroxide could oxidise these cpds to piperonal with the consequent isolation and purification of piperonal; (iii) determine whether or not piperonal would be produced without extraction from pepper; (iv) determine whether or not piperonal could be precipitated from the aqueous liquors by forming the sodium bisulphite aldehyde adduct (which would also quench any excess hydrogen peroxide). But I would not recommend doing any of the above without proper facilities within which to do it.

    Note that I am answering this question with a view to making piperonal rather than some explosive device.

  10. Hi,
    Your blog is really good. very useful to all. Thanks for sharing this..

    Coleus extract Exporters

    Garcinia Manufacturers

  11. I read you blog. Its really amazing. you having very good content. Thank you for sharing this
    Please visit the website:
    Green Coffee Bean Extract Manufacturers

  12. Hi friends ,
    i read your blog, its really good. thanks for sharing this, also see my site

    Car Cleaning Products in India

    Car Care Accessories in India

  13. I read your blog. Its really good. you have nice contecnt and very good information. Its very helpful to all.
    Chondroitin Exporters, Chondroitin manufacturers
    Kindly see my website also.