Breaking Bad : Season 1 : Episode 2 : “Cat’s in the Bag”
Scrambling to deal with the fallout from their encounter with the local drug dealers, Walt and Jesse again turn to chemistry. In this post, I’ll be talking about chirality and how to dispose of a body with hydrofluoric acid.
In this episode’s school class, Walt is talking about chirality – a key concept in organic chemistry and an extremely important consideration in living systems. We usually say that chiral molecules are related as an object and its non-superimposable mirror image (this is written on the blackboard).
The most common example (which Walt gives) is that of your hands. You left hand and right hand are mirror images of each other, but they cannot be superimposed – no matter how you arrange your hands, you cannot align all the parts (fingers, palm, back, thumb etc.) exactly. Many molecules are the same – they exist as two enantiomers, which can have very different properties.
Also on the board behind Walt is an example of a chiral complex ion (a molecule with a central metal ion and weak bonds to several small molecules). We would write it as [Co(en)2(NH3)Br]2+ (en is shorthand for ethylene diamine; H2NCH2CH2NH2) – it is chiral even though the central Co ion has six bonds (rather than the four we’re used to with carbon).
Walt gives a tragic example of different enantiomers having different properties – that of thalidomide. While one enantiomer of the thalidomide molecule is an effective antiemetic (substance that prevents nausea), the other is a powerful teratogen (substance that causes developmental defects). When the drug was first sold in the 1950s, both enantiomers were present (called a racemic mixture) and pregnant women who took it to prevent morning sickness found that their children were born with severe deformities. Even if only the “safe” enantiomer is taken, the molecule will convert to a racemic mixture in the body.
Methamphetamine, the drug around which this season revolves, is also chiral. Only one enantiomer is an addictive psychostimulant; the other (levomethamphetamine) is a decongestant found in products like Vicks Inhaler.
For background information on this topic, see the primer on chirality.
With a dead body about to stink out the RV, rather than dump it (where it may be found) Walt decides to dissolve it in some highly corrosive solution. His chemical of choice is hydrofluoric acid (HF), several litres of which the school supply room just happens to have lying around. This in itself is extremely unusual, as the stuff is so dangerous it would most likely never be used in high school experiments.
Perhaps predictably, Jesse ignores Walt’s instructions to find a large plastic container (the LDPE ones he is looking at are made of low-density polyethylene) and attempts to dissolve the body in the bath upstairs. This kind of body disposal has been done before, but not in a standard domestic bath-for-bathing-in. As Walt later remarks, HF is highly corrosive and will eventually dissolve just about anything except plastics.
Presumably the chemical store would also have had other acids and bases around which would have been just as effective and not so dangerous and difficult to handle. It’s not clear to me why Walt would have opted for HF over the alternatives, but we can’t expect him to do everything perfectly on the first try.
Elements in the credits
|Robb Wilson King||Tungsten|