Deadly Chemicals: (In)famous Poisons Quiz

Answer: KCN

Potassium cyanide (KCN) is an ionic compound consisting of potassium cations K+ and cyanide anions CN-. It is a colourless crystalline solid, similar in appearance to table salt. Due to its good solubility in water and the very small dose required to kill a person, it can easily be disguised in food or drinks, which accounts for its "popularity". It is a salt of hydrocyanic acid (prussic acid), the aqueous solution of hydrogen cyanide (HCN). The latter, under the trade name of Zyklon B, was used in the gas chambers during the Holocaust.

The cyanide ion binds to the iron centre of the enzyme cytochrome c oxidase, which plays an integral role in cellular respiration. This leads to an inhibition (blocking of the action) of the enzyme. So the poison leads to what can be seen as a suffocation on the cellular level, which explains its fast action.

Cyanide is naturally present in bitter almonds, and both HCN and KCN have a distinct almond-like odor. However, the ability to smell it is genetically predetermined and not all people possess it.

Another plant containing cyanide poison is the shrub cassava. It contains substances which can release HCN. Nonetheless, it is a important crop and staple food in many developing nations, being the third largest source of carbohydrates in the tropics, after rice and corn. Due to its potential toxicity, the correct preparation prior to consumption is crucial.

Answer: They are organic substances, typically containing heterocyclic nitrogen atoms.

Alkaloids are organic substances most typically found in plants, though examples produced by animals, fungi and microorganisms are also known. The definition of the term isn't based on a specific type of structure. Still, most feature nitrogen-containing heterocycles (cyclic structures featuring atoms other than carbon). Due to the lone pair of nitrogen (a pair of electrons not participating in a chemical bond), these can act as proton acceptors, in a manner similar to ammonia and amines. Thus, most alkaloids are basic, which accounts for their name - meaning "similar to alkalis".

Some other notable examples of alkaloids are morphine, caffeine and capsaicine (the substance responsible for the hotness of chilis).

Proteins are one of the most important classes of biologically active substances. They feature many different structures and hence fulfil very diverse functions in living organisms. Some important protein types include enzymes - biological catalysis; and receptors - the cellular structures that are responsible for receiving signals from other parts of the organism. Proteins comprise of long-chain polymers, which, in turn, are made up of monomeric building blocks. These latter molecules, known as amino acids, are (mostly) acyclic; furthermore, they contain a carboxyl group (acidic) and an amine (basic) - and as such differ significantly from alkaloids.

Answer: diarsenic trioxide, As2O3

Diarsenic trioxide, also known as white arsenic, was a favourite with the European nobility, including (allegedly) members of the Borgia family. Since exposure to small, non-lethal amounts of the poison over time increases the dose needed to kill a person (a process known as mithridatism), some rulers are said to have practised it as a means of protection. White arsenic was also a component of Aqua Tofana, a poisonous mixture used in the 16th and 17th century by Italian women wishing to murder their husbands. There are even some rumours that it was used to kill the famous compozer Mozart, though no evidence to that effect actually exists.

The Marsh test, which made possible the proof of death by arsenic poisoning, relies on the conversion of As2O3 to the gaseous arsine (AsH3). The latter is unstable and quickly decomposes under formation of elemental arsenic, which can be observed as a black powder.

Arsenic disrupts the production of adenosine triphosphate (ATP), a molecule that plays a vital role in the transport and storage of energy in living organisms. Death results from a multi-system organ failure, notably affecting the digestive and nervous systems, as well as the liver and kidneys.

While lead oxide is indeed poisonous, lead itself is a metal, rather than a metalloid. Of the provided wrong answers, only silicon is a metalloid. Still, its dioxide isn't toxic - it's found in the mineral quartz and is the main component of sand and glass. The oxide of the metal aluminium is also non-toxic and found in nature in the form of the mineral corundum and the gemstone ruby.

Answer: mercury sulfide, HgS

The solubility of mercury sulfide is roughly 0.2 yg per litre (a yoctogram is 10^-24 grams, or 0.000000000000000000000001 grams) - which is why it is considered insoluble in water. Since metabolic processes take place in aqueous medium (the human body being made out of approximately 2/3 water by mass), HgS can't easily be taken up by the organism. Accordingly, a common procedure for cleaning up minor mercury spills involves the use of powdered sulphur, which reacts with Hg to form HgS. The substance can be found in nature in the form of the mineral cinnabar, which in powdered form comprises the red pigment vermilion.

By contrast, all three wrong answers are considered highly toxic. The pure metal, while not soluble in water, has a very high vapour pressure, i.e. is highly volatile. As such, it can be be absorbed via inhalation. Mercury dinitrate is, like most nitrates, water-soluble. Its use in the treatment of fur to manufacture felt has probably lead to the existence of the phrase "mad as a hatter", since a symptom of chronic mercury poisoning is mental confusion.

The most dangerous of the three, dimethylmercury can be toxic in amounts as small as 0.1 mL. It is not only a highly volatile liquid, but can also pass through most types of protective gloves withing seconds and be absorbed through the skin. This was tragically discovered in an accident in 1996, when Dartmouth chemistry professor Karen Wetterhahn spilled a few drops of the substance on her hand while wearing protective gloves. Her death of acute mercury poisoning less than a year later was a shock to the scientific community, since she had followed what was at the time believed to be the necessary safety procedures.

The toxicity of mercury is caused by its reaction with the vital micronutrient selenium, which helps prevent oxidative damage to the brain and endocrine organs. Accordingly, mercury poisoning primarily affects the nervous system.

Answer: The oxidation state of chromium.

The connection between the elevated cancer rate and the groundwater pollution in Hinkley, CA was investigated by legal clerk Erin Brockovich. The source of Cr (VI) was the nearby natural gas compressor plant operated by the Pacific Gas and Electric Company. Improper storage of solutions used for rust prevention lead to the contamination. The incident is famous both for the size of the settlement - the largest ever in a direct-action lawsuit in US history, as well the film depicting the events, which was released in 2000 and won actress Julia Roberts an Oscar for her portrayal of Brockovich.

Chromium(VI) describes substances containing Cr in the oxidation state of +6, most typically salts featuring the chromate (CrO4 2-) or dichromate (Cr2O7 2-) anion. An oxidation state denotes the charge an element would have if all bonds in the respective substance were considered to be ionic. Since this is a model concept, for polyatomic ions with covalent bonds the oxidation state differs from the net charge of the ion - in this case +6 and 2-, respectively.

Chromium is a curious example of toxicity depending on the oxidation state. While the other typical oxidation state, Cr(III), is being studied for possible biological importance as a trace element, Cr(VI) is both acutely toxic and, as the above example shows, a dangerous carcinogenic.

The atomic number of an element, which is identical to the number of protons in the nucleus (chromium has 24), is typically given as a subscript on the left-hand side of the element's symbol. The half-life - the time it takes for half the mass of a given radioactive isotope to decay, is a characteristic of its stability and can be found in special reference tables.

Answer: two

In chemistry, the nomenclature (the set of rules regarding naming) is regulated by the International Union of Pure an Applied Chemistry (IUPAC). A typical feature is the use of prefixes to denote the number of atoms or atomic groups present in a substance. These include "mono-" (one), "di-" (two), "tri-" (three) and "tetra-" (four). A well-known example of this use is the name carbon dioxide (CO2), the gas added to carbonated drinks, which is also an environmental hazard due to its action as a greenhouse gas.

PCDDs are dangerous not only because of their acute toxicity, but also due to the fact that they bioaccumulate, i.e. are stored in the organism (predominantly in the fatty tissues) and accordingly can have long-lasting effects. Dioxins cause damage to many organs and tissues, such as the skin, the nervous and immune systems, and are also considered to be carcinogenic.

One of the most notable cases of dioxin poisoning in recent history is that of the former Ukrainian president Yushchenko during his presidential campaign in 2004. As PCDDs aren't substances people typically get exposed to in their day-to-day lives, and due to Yushchenko being a high-profile political figure, some claims exist that the poisoning was a politically motivated attempt on his life. Although he survived his exposure to the toxin, he hasn't been able to fully recover.

Answer: an ester group

An important feature of curare alkaloids as arrow poisons is the fact that their action results from a delivery directly into the bloodstream, so they aren't absorbed through ingestion. As a result, a hunter could kill an animal by shooting it with a curare-laced dart without fear of poisoning from eating its meat.

The toxicity of curare poison comes from its action on nerve cells (neurons). Normally, upon receiving a nerve impulse, acetylcholine is released by a neuron and binds to certain receptors in the neighbouring cell. This causes a signal to be generated in and thus conducted to the second neuron. Curare poisons, which have some structural similarity to ACh, bind to the receptors without releasing a signal, blocking the transmission.

The structure of ACh is given by the formula CH3COOCH2CH2N(CH3)3 +. The reaction between an organic acid RCOOH and an alcohol R'OH (with R and R' denoting organic residues) produces water and the functional group RCOOR' , known as an ester. An ether ROR' is produced upon reaction of two alcohol molecules; a peptide RCONH2R' is a special type of amide formed between amino acids; an aldehyde can be formed by oxidation of some alcohols and has the functional group RCHO.

Answer: chlorine, Cl2

The name of the element is directly related to the colour of gaseous chlorine and is derived from the Greek word for green-yellow. The visibility of an approaching greenish cloud served soldiers as a warning sign, though, at first, little could be done to prevent the effects of the gas. As the action of chlorine became better understood, protective measures were taken - at first rudimentary (a wet cloth to absorb the gas), later leading to the development of the first gas masks.

Chlorine is a very aggressive substance, as it can readily act as an oxidising agent on contact with tissues, or else produce a mixture of hydrochloric acid (HCl) and hypochlorous acid (HClO) upon reaction with water in the cells. It irritates the eyes and the mucous membranes of the respiratory tract, causing lasting damage even to people surviving the attack.

Phosgene is another poisonous gas, first used in World War I by the French. Unlike chlorine, it is colourless, which made it more difficult to detect and so more effective to use.

Dichlorodifluoromethane, also known under the trade name Freon-12, is a type of chlorofluorocarbon (CFC). CFCs have very low reactivity and as such don't pose a direct threat to human health. However, they have an immense impact on the environment, as they are the major cause for the depletion of the ozone layer.

Calcium dichloride is neither a gas, nor toxic. It is a colourless crystalline salt, which is commonly used as a desiccant due to its hygroscopic nature.

Answer: lipophilicity

The term for good solubility in fats and oils, "lipophilicity" derives from the Greek words for fat (lipos) and friendly (philos). By contrast, "lipophobicity" comes from "phobos", meaning fear - so it characterises the exact opposite quality. In turn, "hydrophilicity", or "love of water" denotes a good solubility in water. A substance that displays both lipophilic and hydrophilic qualities is called "amphiphilic", from "amphis", meaning "both".

The solubility of substances in water or lipids (fats, oils and related compounds) is directly related to the polarity of their molecules. In order to dissolve, a chemical needs to interact with the particles of the solvent. As interactions between polar molecules differ significantly in strength from those between non-polar molecules, polar substances dissolve easier in polar solvents, such as water. Non- or not very polar substances are better soluble in non-polar compounds, such as fats. If a molecular structure contains both polar and non-polar groups, as is the case with soap, it can interact with both types of solvents, making it amphiphilic.

Sulfur mustard, with the chemical formula (ClCH2CH2)2S, is the most commonly used mustard gas. During World War I its main application was as a disabling agent - as in lower dosages it causes very painful chemical burns, rather than directly killing the affected soldiers. Since the polluted areas remained contaminated for several days, this prevented enemy troops from advancing.

The action of mustard gas is based on the elimination of a chloride anion (Cl-), producing an electrophile ("electron-loving") - a highly reactive positively charged particle. It disrupts cellular division by directly reacting with DNA. This leads either to cell death - the reason for the painful blisters, or else, if the cell survives, causes cancer due to the generated mutations.

Answer: True

The nerve agents sarin, soman and tabun are classified as Schedule 1 substances according to the Chemical Weapons Convention (CWC) - substances that are used predominantly or exclusively as chemical weapons. The 190 countries bound by the CWC (status: 2013) are prohibited from producing or storing chemical weapons.

Tabun, sarin and soman were initially developed in the 1930s and 1940s by German scientists - and are consequently known collectively as G-series nerve agents. Initially discovered in an attempt to produce potent insecticides, they were soon found to be highly toxic to humans. While plans for their use during World War II existed and their production was commissioned, none were applied in battle at the time. Still, there have been some later instances of nerve agents use, often by terrorists or insurgents, but also during wartime conflicts, such as a sarin attack in 1988 during the Iran-Iraq war.

Nerve agents act as inhibitors to the enzyme acetylcholinesterase, which is responsible for the breakdown of the neurotransmitter acetylcholine (ACh). Normally, after a signal is transmitted, ACh is degraded by the enzyme and the impulse stops. When this process is blocked by the nerve agent, ACh accumulates, leading to a continuous transmission, which results in non-stop muscle contractions. This causes spasms and, due to the effect on the muscles involved in breathing, death by asphyxiation.

On its own, atropine - an alkaloid found in belladonna (deadly nightshade), is a potent poison, similar in action to curare. It blocks the binding site (receptor) for ACh and thus prevents the transmission of nerve impulses. However, this effect can be vital as an antidote for nerve agents. Though it doesn't stop the buildup of ACh, it blocks it by not allowing it to bind. As such, it counteracts the effect of the nerve agents, and is accordingly applied as a means of treatment.

Answer: sulphur

Sodium thiopental is a type of rapid-onset barbiturate. In a typical US procedure, it is used to induce unconsciousness in the person put to death during capital punishment, before a drug is applied to paralyse muscles, including those necessary for breathing, and a potassium salt solution is administered to disrupt heart rhythm and stop the heartbeat.

Sodium thiopental also has important medical uses, including anaesthesia, medically induced coma and treatment of epileptic seizures. As such, it is produced by several pharmaceutical corporations, many of which are based in Europe. Since EU-countries do not practice capital punishment and are openly opposed to it, in recent years there have been multiple bans on export of the chemical to the US, unless it can be guaranteed it wouldn't be used for lethal injections. While this hasn't completely stopped death penalties from being carried out, it has caused some delays and difficulties.

The prefix "thio-", from the Greek word for sulphur, is used to denote the presence of the element in both inorganic and organic substances. Since sulphur and oxygen are in subsequent periods of the 16th group of the Periodic table, they form many analogous compounds. Thus, in many cases "thio-" is used to show the substitution of an O-atom with a S-atom. Examples include the thiosulphate ion S2O3 2- and the sulphate ion SO4 2-; or the thioalcohols (thiols) RSH and alcohols ROH (where R represents an organic residue).

Sulphur (UK)/sulfur (US) is an example of alternative spellings of an element's name in different variations of English. Other such elements are aluminium (UK)/aluminum (US) and caesium (UK)/cesium (US). The UK spellings stem from the original Latin names, whereas the US versions are simplified to better reflect pronunciation.

Answer: The provided answers can be used as synonyms.

Other than their effect on plane-polarised light, optical isomers have identical physical properties and mostly identical chemical reactivity. This is due to the fact that their structures are the same in terms of functional groups and general connectivity of the atoms. The only structural difference between two enantiomers is the spacial arrangement of said groups. This accounts for the name "chiral compounds" from the Greek word "kreir" (hand) - as each hand has five fingers in a defined sequence, yet the specific arrangement of the left and right hand mean the two are mirror objects rather than identical.

The difference in spacial structure has an impact on the biological properties of enantiomers. To carry the hand metaphor further, in the same way a left hand wouldn't fit a right-hand glove, one enantiomer won't fit the active site of an enzyme designed to fit the other. As enzymes act as biological catalysts, the action of a particular chiral compound can heavily influence metabolism. This was tragically discovered in the late 1950s and early 1960 with the drug thalidomide (German trade name Contergan). Marketed as a mild sedative for pregnant mothers, it lead to 10000 children in 46 countries being born without, or with severely deformed, limbs. It was later shown that while the (R)-enantiomer does indeed have a sedating effect, (S)-thalidomide influences a completely different metabolic pathway, leading to the teratogenic (congenital defects-causing) action. The scandal prompted the introduction of more extensive testing and stricter rules regarding the use of chiral compounds in medicine.

Socrates is considered to be one of the most influential philosophers of all time, particularly for the development of the "Socratic method" of thinking - using inquiry and debate to stimulate critical thinking. However, his criticism of Athenian democracy, as well as his suggestion that leading society figures lacked wisdom caused people in positions of power to turn against him. As a result, he was tried and found guilty of corrupting the minds of young Athenians, as well as being impious, i.e. not believing in the gods of the state. His death, brought about by drinking an infusion of poisonous hemlock, was described and discussed in several works of his contemporaries, most notedly in a series of dialogues by Plato.

Answer: haemoglobin

Haemoglobin is a protein consisting of four polypeptide chains, each containing an iron centre. The iron(II)-cations normally bind to oxygen (O2) and carbon dioxide (CO2) molecules, thus facilitating their transport from and to the lungs, respectively. Carbon monoxide (CO) acts as a potent poison, because the strength of its bond to haemoglobin exceeds that of both oxygen and carbon dioxide. As a result, the binding sites are blocked and even if the affected person inhales oxygen, it can't bind, leading to a suffocation on a cellular level.

The described mechanism of action is quite similar to the one given for cyanide in question #1. Even though two different molecules are affected by two different poisons, there are reasons for the similarities. On the one hand, carbon monoxide and cyanide are very similar in structure. Both feature a carbon atom bound to a heteroatom - oxygen (O) and nitrogen (N), respectively. With O and N being neighbours in in the periodic table and cyanide carrying a negative charge, both structures end up having an identical number of electrons - described as isoelectronic species. This property leads to very similar binding patterns.

The other contributing factor for the similar actions of CO and cyanide is the structure of the proteins themselves. Like many proteins, haemoglobin and cytochrome c oxidase contain a non-peptide structure (a cofactor), which is responsible for their function. With both of these proteins, the cofactor is heme - an iron(II)-cation bound to a type of heterocyclic ring, called a porphyrin.

Porphyrins are an important class of heterocycles. Other than the two examples mentioned above, porphyrin centres are also contained in other vital proteins, such as haemocyanin - the haemoglobin-analogue found in some inverebrates; and chlorophyll - the green pigment which facilitates the first step in plant photosynthesis. Unlike the iron-containing heme, haemocyanin contains copper(I)-cations, wheres in chlorophyll the porphyrin is bound to magnesium(II).

A famous case of carbon monoxide poisoning is the suicide of South African photojournalist Kevin Carter in 1994. He was well-known for his work as part of the so-called "Bang-Bang club", a group of photographers documenting the violent unrests preceding South Africa's post-Apartheid first democratic election. Carter also garnered international fame for his Pulitzer Prize-winning photograph of a starving girl being stalked by a vulture, during the famine in Sudan in 1993. Sadly, the horrors he witnessed daily in his home country, as well as guilt for not having helped the little Sudanese girl, led Carter first to a drug addiction and, in the end, resulted in him taking his own life. Kevin Carter's story is described by one of his colleagues from "The Bang-Bang Club", Greg Marinovich, in an eponymous book.

Answer: It contains a binding site for the amino acid cysteine.

Cisplatin - chemical name cis-diamminedichloridoplatinum(II), is a coordination compound (coordination complex) with the chemical formula [Pt(NH3)2(Cl)2].

The name "complex" refers to the fact that the species it is made out of - platinum(II)-cations (Pt 2+), chloride anions (Cl -) and ammonia molecules (NH3) are, unlike atoms, stable structures in their own right - making the compound they make up together a more complex structure. The term "coordination" stems from the way such compounds are built. Electron-rich molecules or ions, known as ligands, are ordered around and bound to one or more metallic centres. The ligands act as electron pair donors and bind covalently to the metal, which in turn is the electron pair acceptor.

In the case of cisplatin, the metallic centre is the platinum(II)-cation (Pt 2+) and the ligands are ammonia (NH3), donating its lone pair, as well as chloride anions (Cl -). There are two of each of these species per one Pt(II)-ion. They assume a square planar coordination, i.e. the ligands are based in one plane on the corners of a square, with platinum in the centre (at the point where the diagonals intersect).

This structure allows for two different geometries: each of the two pairs of ligands can be either places on neighbouring corners (the cis-form), or else on opposing corners (the trans-form). Of these two, the cis-form is the one exhibiting important medicinal properties - which leads to the name Cisplatin. The amino acid cysteine (note the different spelling - with a Y!) is in no way involved with the structure or mechanism of action of the drug.

Cisplatin kills cancer cells by binding to the cell's DNA. This leads to different parts of the DNA strand to be bound to each other (a phenomenon known as crosslinking), thus preventing the DNA from replicating (being copied). This, in turn, inhibits the cell's ability to divide itself. Furthermore, the body's regulatory mechanisms recognise the affected cell as damaged and apoptosis - the cell's programmed death mechanism - is triggered.

The reason for cisplatin's relative selectivity towards cancer cells is the fact that they are the ones that divide the fastest. Unfortunately, healthy cells that also divide quickly - such as those in the lining of the stomach and in hair follicles, are affected in a similar manner. This explains the drug's negative side effects, such as nausea and hair loss.

Modern cancer treatments aim to improve the selectivity of the drugs used in chemotherapy and specifically target only the affected cells, without harming healthy tissues. However, since there are many different types of cancers, research on the specific processes involved is time-consuming and costly. Hence, if you happen to be on the lookout for a charity to support, helping fund a cancer research facility is certainly a very good option!

Answer: Each of these substances can be poisonous

"All things are poison and nothing is without poison; only the dose makes a thing not a poison.". This expression, often condensed to "the dose makes the poison", was formulated by Paracelsus, a Swiss-German scientist who is widely regarded as the founder of the field of toxicology. Indeed, for a living organism to function properly, what is most important is maintaining a balance - a property known in biology as homeostasis. Since any substance is capable, in sufficiently high quantities, to disrupt this balance, it can thus function as a poison. However, what we commonly refer to as toxins are substances for which this sufficient amount is very low and which, mostly, have no other function in the human body.

Perhaps most surprising of the above choices is the poisonous effect of water - after all, approximately 2/3 of the mass of a human body is made up of this vital liquid. One of water's key properties is its function as a solvent - dissolving important substances, such as minerals (electrolytes) and sugars. When large quantities of water are ingested too quickly and the excess isn't removed fast enough as urine or sweat, this causes dilution of all body fluids, such as blood, saliva, lymph etc. As a results too much water enters the cells, which have a higher electrolyte concentration. This can lead to nausea, dizziness and confusion from increased pressure to the brain, muscle cramps and, in some extreme cases, even death. A famous example: the passing of American pop artist Andy Warhol is believed to have been caused by water poisoning from being administered too many fluids during recovery from a gallbladder surgery.

The opposite mechanism is responsible for the toxicity of table salt. When the concentration of sodium chloride in the bodily fluids is too high, water is removed from the cells, leaving them dehydrated and shrunk. Such cells can't perform their normal function, which is especially dangerous when it affects nervous cells.

Aspirin is a common drug, used to treat pain inflammation as well as to prevent heart attacks and stokes. However, in higher doses it overstimulates the respiratory centre in the brain, which causes a condition known as respiratory alkalosis - a reduced arterial concentration of carbon dioxide. Since the latter is necessary for maintaining the acid-base balance in the body, the condition leads to nausea and neurological symptoms. Still, the lethal dose of Aspirin is comparatively high, ~300 mg per kg body weight. Accordingly, most cases of severe Aspirin poisoning have been caused by voluntary ingestion of too-high doses, mostly in suicide attempts.