Aldehydes are more easily oxidised than alcohols, and if you remember alcohols are oxidised TO aldehydes. So if you’re adding a strong oxidising agent to excess (think acidified dichromate/manganate – by the way both relatively harmless to drink as they’re readily excreted from the body.) it can look like it goes straight from alcohol to carb acid. (these agents can only be used to tell the difference between alcohols/aldehydes and ketones)

But it doesn’t! What tricky organic molecules! With aldehydes you can add things like [Ag(NH₃)₂]+ – ammoniacal silver nitrate – or the “Tollens’ reagent” and they will be reduced to a fine black precipitate of silver. Don’t try making jewellery by collecting silver this way. I mean it when I say fine. You can also add something with Cu2+, used in the Benedict and Fehling tests. The copper is reduced to a brick red molecule, which doesn’t happen in alcohols or ketones.

And while we’re talking about tricky organic molecules, methanal or HCHO is formaldehyde, and ethanal is acetaldehyde. Propanone is commonly known as acetone.

Another good way to tell aldehydes and ketones apart is that aldehydes smell really bad and ketones smell quite sweet or pleasant, or like nailpolish remover.

Short-chain aldehydes and ketones are soluble in water, and they also tend to be soluble in non-polar solvents (such as octane). Their boiling points are lower than alcohols and higher than alkanes.

The much (well, twice)-mentioned acyl chlorides (or acid chlorides) end in –anoyl chloride. They are colourless and volatile, and smell. Really smell. There are probably other –anoyl halogens, but they aren’t as crazily reactive as acyl chlorides are. They are usually formed with special reagents: PCl5, phosphorous pentachloride, PCl3, phosphorous trichloride, and SOCl2, thionoyl chloride. (These ARE poisonous, so don’t try eating or drinking them).

Substitution reactions are super-fast with acyl chlorides. They can react with water to form a carboxylic acid and hydrogen chloride as a gas, with alcohols to form an ester and hydrogen chloride, and with ammonia to form an amide and ammonium chloride. (HCl cannot be formed in the last one as the amide is basic, making the mixture alkaline).

Acyl chlorides also react with amines to form a secondary amide (don’t forget the N- at the beginning!) and methyl ammonium chloride salt.

Speaking of amides, they’re all white crystalline solids and don’t smell much at all. Their functional group is –CON– with the same naming system as amines. I remember it because amines have a mean (nasty) smell and you don’t mind amides.

When you heat ammonium salts it makes amide and water. You can also form them by reacting an ester with ammonia in water, or reachting an acyl chloride with excess ammonia (or a primary amine!). Amides don’t react with acids and appear neutral – but amines are basic.

Hydrolysis of amides can occur in acid to form carboxylic acid, or in base to form carboxylate ions. Diamines and acyl chloride (or dicarboxylic acids) react together to form a polyamide, a large molecule connected by -C(=O)-NH-

If using acyl chlorides, HCl is lost when each amide bond is formed. This makes it a condensation polymer, just like polyesters.

Amino acids consist of two functional groups: NH2 (amino group) and COOH (carboxylic acid group). As the NH2 group is basic and the COOH group is acidic, amino acids tend to exist as an ion: +NH3CHRCOO-

This is called a zwitterion.

As a carbon in amino acids (the “alpha” carbon) is connected to four different groups and so is asymmetric, it can show optical isomerism. This is when the amino acid forms something else when reflected in a mirror and they are called enantiomers. Enantiomers reflect polarized light in opposite directions – and only one of the two optical isomers of an amino acid can be used by living creatures.

Usually amino acids will have a scientific name and a common name. For example, alanine is CH3CH(NH2)COOH or 2-aminopropanoic acid. Proteins and polypeptides are naturally occurring polyamides from amino acid monomers.

This brings us to the end of organics. Hopefully you’ve absorbed some of that – you can now have the fun of reading the backs of packages and being able to know exactly what those molecules look like.

The part connected to the oxygen is named first, so: CH3-O-(O=)C-CH3 is methyl ethanoate whereas CH3CH2OOCH is ethyl methanoate.

They are colourless, have lower boiling points (because they don’t have hydrogen bonding – remember the van der Waals forces?) and aren’t very soluble.

Esterification (carb acid and alcohol) is usually done under reflux, using concentrated sulphuric acid as a catalyst. Reflux means vapours are returned to the reaction mixture. When using an acyl chloride and an alcohol, fractional distillation occurs. The reaction is fast and a lot of ester is produced. It’s the most efficient way to do it.

Hydrolysis is reverse esterification. In acidic conditions, it creates a carboxylic acid and an alcohol, and in basic conditions is creates a carboxylate ion or salt.

Fats and oils are triesters of glycerol, three esters flying out like flags from a three-carbon backbone. Saponification is what chemists call soap making and it involves the alkaline hydrolysis of these triesters. And that means adding a base (e.g. sodium hydroxide, NaOH) to hydrolyse a trimester, resulting in an alcohol (glycerol) and three carboxylate ions.

Let me know if I haven’t explained some words? I lose track sometimes.

If you add ammonia to an ester, it v e r y s l o w l y forms an alcohol and a primary amide. Not the best way to make either of those.

When glycerol undergoes esterification with three fatty acids, it becomes a triglyceride. And a polyester is a large molecule made up of monomers joined by ester bonds(-O-), diols and dicarboxylic acids (HOOCCOOH). Polyester is a condensation molecule as H2O is lost when each ester bond is formed.

We’re zooming through these, aren’t we? Of course, it requires some effort on your part. I think this is what education misses out on. If kids fail, it’s because they haven’t been taught well. Not because they spent all their time doodling in the margins of their books. I’d also like to point out that it’s a lot easier to make mistakes in the classroom than in life. Mixing up, say, short-chain carb acids and esters make the lab a bit smelly. Mixing them up later, when you’re making perfumes, makes you fired.

Interlude over. (I should get some good jokes I can insert when it’s a bit dry. So, rotational velocity is measured in radians but hey, how does a mathematician pick his nose? He works it out with a pencil!)

Amines (or aminoalkanes) are pretty important. They have a nitrogen at one end, so you count the carbons from that end. They’re like alcohols in primary, secondary, and tertiary having one, two, and three carbons attached to the N atom respectively. Short-chain amines also smell quite nasty – “fishy”.

They occur from the breakdown of protein, and are especially noticeable in fish. Most fish have enzymes (proteins that make reactions happen) in their gut that can break down fish protein and create amines, so it’s important to gut a fish as quickly as possible so they don’t start smelling bad.

Smaller amines are soluble, and amines react with acids to form salts – this reaction takes away the fishy smell, which is why we put lemon juice on our fish (it means amines are also basic). When NH3 and haloalkanes react in alcohol, we end up with an amine.

For secondary and tertiary amines, the name starts N-methyl­aminopropane. The root of the name is from the longest carbon chain. N,N-dimethylaminopentane.

As you can guess, as we get further in these things get a little bit more complicated. But hey! Before you wouldn’t have even understood those names up there. Now, at least, you know that they’ll probably smell bad. What does that mean? There’ll be a sweet-smelling thing in there somewhere too.

We are based on carbon. Organic chemistry is based on carbon. Pure carbon is a black solid. Impure carbon is pretty much everything alive or edible.

I mean, glucose, the base of respiration which is why we are alive, is C6H12O6.And then propane (ever seen King of the Hill?) is C3H8. That’s it. Of course, by seeing the –ane at the end and the prop- at the beginning, we know immediately there are three carbons connected by single bonds. We didn’t?

Carbon can have four bonds. Hydrogen has one. Oxygen can have two. We are now set up.

For organic chemistry, we need to learn a bit of vocabulary. So bear with me a bit, you can refer back to here whenever you need.

1……..2 …….3 ……4 …..5 …….6

Meth- Eth-     Prop-    But- Pent-  Hex-

Methyl Ethyl Propyl Butyl

Cl ………F…….. B …….I

Chloro- fluoro- bromo- iodo-

So if you have CH3-CH2-CH3, it’s propane. Hydrogen fills all the gaps when there aren’t enough bonds. As you can see, there are only single bonds between the carbons. This makes it an alkane.

Alkanes float and readily burn in air (easy combustion). Up to and including butane, they are a gas at room temperature, and from pentane to uh… 15-carbons, they are volatile liquids. Volatile means they could turn into a gas at any moment – have you ever wondered why the smell is so bad at petrol stations? It’s not because people suck at filling up their cars. It’s because the alkane in the petrol is volatile.

Octane is an alkane. C8H18, if you’re interested. Alkanes are the simplest organic molecules, and by simplest I mean most boring.They don’t react with much, and when they do, they react v e r y s l o w l y.

Compare that with alkenes. They’re just the same as alkanes, except you end –ene and have a double bond. So propene is CH2=CH-CH3.

Oh, a good point to make here is “functional groups”. A functional group is whatever gives the organic molecules its name. So for alkenes it’s the double bond – 1-butene (or but-1-ene) is CH2=CH-CH2-CH3. If there is no functional group, you start counting from the end with the “side chain”. A side chain is a chain of carbons coming off the side, so if you have 2-methylbutane it looks like CH3-CH (CH3)-CH2-CH3.

A good way to tell alkenes and alkanes apart is by using bromine water. If you add bromine to an alkane, it undergoes a substitution reaction, which means a hydrogen atom gets torn off and replaced with Br. This results in a haloalkane and hydrogen bromide.The reaction takes place slowly, and only under UV light.

On the other hand, adding bromine water to an alkene is an addition reaction. See the double bond? That goes away and the carbons on either side bond to Br, resulting in dibromo-whatever. They both end up with the same product, but the alkene takes a much quicker route.

Alkenes can have geometric isomerism, which means two molecules can have the same molecular formula and different orientation space. It’s because they can’t rotate over the double bond, and I can’t draw it here unfortunately, but I hope you’re getting this. One group has to be the same on both carbons and one group must be different. So CH2CH2 wouldn’t have isomerism but CHClCHCH3 would.

The two types are cis for when the same groups are on the same side (like “sisters”), and trans for when they are on different sides. Yeah, just like trans fats.

When heaps and heaps of alkenes bundle up together, they might lose their double bonds and start bonding to each other instead. This makes a polymer and they get names like polyethene, polybromoethene, depending on what the monomer (starting molecule) is. It looks like -(CH2CH2)-n so pentene would look like -(CH(CH3)CH2)-n They always join over the double bond.

Another neat reaction alkenes undergo is oxidation. So a good alkene/alkane test is to add some acidified potassium permanganate (it’s purple) and see if the purple colour disappears. If it does, congratulations, you now have an alcohol! If you oxidised pent-2-ene, you’d end up with 2,3-pentandiol. This is a diol because it has two functional groups of OH. An alcohol with three functional groups is… yep, it’s a triol!

An alkyne is just like an alkene except it has a triple bond. In addition reactions, more is added because it has more bonds to fill up. They don’t come into play much (have you ever heard of propyne?) so let’s keep going.

Alcohol! Their functional group, you’ll see above, is OH. So ethanol is CH3-CH2-OH (OH bonded to C). There are three types of alcohol and what it is determines how it reacts. This one is quite interesting as it ends in –ol, and there are plenty of words ending in –ol on the back of packages.

Primary alcohols have one carbon bonded to the carbon bonded to the OH. So the ethanol above is primary.Secondary alcohols have two carbons bonded to the carbon bonded to the OH. So butan-2-ol (CH3CH2CH(OH)CH3) is a secondary alcohol.Tertiary alcohols have… you can guess. 2-methylbutan-2-ol is an example, CH3CH2C(CH3)(OH)CH3

Boiling points are higher than corresponding alkanes, and short chain molecules are soluble because of the polar C-OH bond. This is why you can water down wine. To make alcohols, you can have a substitution with a haloalkane and NaOH or KOH. So RCl (where R stands for the Rest of the molecule) + NaOH –> NaCl + ROH. It also does this the other way – ROH + PCl5 –>RCl + PCl4OH

You can also hydrate an alkene (and dehydration or elimination of alcohols results in alkenes).Or, if you’re really stuck, you could try the anaerobic fermentation of sugars. After all, that’s how it’s been done for thousands of years!

There’s propylene glycol in my moisturizer. Luckily I know that glycol is ethan-1,2-diol (and now you do too! Glycerol is propan-1,2,3-triol) and it must have a double bond in there. So it ‘s CH2(OH)-CH(OH)=CH(OH) doesn’t look so scary now, eh?

If you oxidise a primary alcohol (with acidified potassium permanganate or acidified potassium dichromate), it becomes an aldehyde. We’ll get to them.

On oxidising a secondary alcohol, it becomes a ketone. We’ll get to those at the same time as aldehydes.

Carboxylic acids (excuse my inconsistent formatting!) are organic acids. Their names end in –anoic acid and their formula end in a double bonded O and an OH. Propanoic acid is CH3CH2COOH.

They undergo general acid reactions, and taste sour like normal acids. (incidentally, sour tasting is due to the opening of ligand-gated ion channels in your taste neurons). They include fatty acids! Fatty acids are long, straight and insoluble. They tend to remain as a liquid unless they are (mono/poly)unsaturated. Unsaturating a fatty acid adds a kink into the chain, which makes them sit close to one another. It also makes them more likely to decompose into shorter carboxylic acids. Shorter carboxylic acids have really nasty smells and tastes.And with less than four carbons, they’re soluble.

If you mix a carboxylic acid and an alcohol, it makes an ester (esters smell sweet, so it might be something you want to do if you’re stuck with a short-chain acid!)R-COOH + R’OH –>R-C(=O)-O-R’ + H2O

Carb acids also undergo substitution, which turns them into a kind of haloalkane – acyl chlorides (end in –anoyl chloride) RCOCl. They react strongly with water to form carboxylic acids again, so if you use HCl you’ll never make one. You have to use something like PCl3.

Carb acids can also form ions – PropANOATE is CH3CH2COO-

I’ll leave esters till next time.

Some atoms are really good at attracting electrons towards them. It depends on a lot of things, such as how many shells they have (their row on the periodic table) which also affects how far from the nucleus the outermost electrons (“valence” electrons) are and how many protons they have (their atomic number). Now that you know that, I’m sure you can work out how these trends go. You’re intelligent people.

For the cheaters: More electronegative going left to right, and bottom to top, ignoring the noble gases. Fluorine is the most electronegative – and I always have a mental image of a fluorine atom telling its electrons “No, there’s no way you could do that, don’t even bother trying, you’ll just fail.” What a pessimist!

A covalent bond might be polar or non-polar. If it’s polar then one end is slightly more negative than the other end, due to the difference in electronegativities. The C-F bond is polar, but the shape of CF₄ is tetrahedral, which means it is symmetrical, so the overall molecule is not polar. But the H-Cl bond is also polar and the shape is linear, because there are only two atoms involved, so the overall molecule is polar, with differently charged ends or “dipoles”.

If you want to know about shapes, let me know. I think they’re a useless amount of memorizing. But it’s about interest here! I am the geek of the people!

Seeing as covalent bonds result in separate molecules, they have intermolecular forces (between the molecules) as well, called “van der Waals” (van de Vahls) forces.

With non-polar molecules such as CF₄ or CO₂, the buzzing electrons can concentrate in an instant in one place resulting in a temporary dipole that induces polarity in nearby molecules, resulting in a chain of temporary dipoles, attracting them for an instant. This is why, if you cool gases such as N₂ down, slowing the buzzing of the electrons right down, they form a liquid.

And liquid nitrogen can be used to make instant ice-cream, which apparently tastes just as good as the stuff that takes two hours at home. But if it freezes your hand, it will probably drop off. Be careful around very cold things. Like liquid nitrogen.

Polar molecules, like HCl, have permanent dipoles, so the positive end of one molecule attracts the negative end of a nearby molecule. This is stronger than temporary dipoles because it is constant and there is usually a greater difference between ends than in the temporary dipole.

Hydrogen bonding is like a superpowered version of permanent dipoles. When H bonds to nitrogen, oxygen, or fluorine, the large difference in electronegativity results in a near-empty hydrogen orbital. It only had one electron to begin with! Poor hydrogen… it attracts the negative end of a nearby molecules very strongly and so is the strongest van der Waals force.

The van der Waals force involved will determine the state of a non-metal covalent molecule.

This leads me to organic chemistry. Next stop, propane.

But! We can get started on the different types of bonding present in the world around us. And it’s not just the type that occurs when you have a heartfelt conversation with someone – we’re talking microscopic.

If you get out your periodic table now (I keep mine on my desk for easy reference) you might see that there’s a diagonal line running across it on the right-hand side. It starts just below Boron (number 5) and finishes to the left of Polonium (84). That line separates the metals (left) from the non-metals (right). The elements along that line have some metallic properties and some non-metallic properties.

“But”, you say, “since when was calcium a metal? And sodium? That’s in table salt!” I hear you. I said exactly the same thing. Yes, everything to the left of that line is a metal. Even calcium. Even sodium. And when it comes to metals, sodium is one of the cooler ones. If you ever have the opportunity to lie your hands on a piece, throw it into a bucket of water and retreat to a safe distance.

Metals by themselves undergo metallic bonding. It’s a regular arrangement of the nuclei surrounded by a mobilized sea of delocalized electrons. Phew! That sounds complicated eh? It means the electrons have stopped belonging to any one atom. They move around wherever they please, and as charged particles, their freedom means metals can transmit electricity. Since the nuclei can move over each other and don’t object as long as they don’t get too close, this means we can shape metal. Even though this might make it seem like metals don’t have strong attractive forces, they have high melting and boiling points because the nucleus and electron still have quite strong forces tying them together.

Between a metal and a non-metal, you get ionic bonding. This occurs when one ion gains electrons (to become negatively charged) and one loses them (to become positively charged) – for example Na+ + Cl- –> NaCl, or a sodium ion plus a chloride ion makes sodium chloride.

Incidentally, chemists give some things different names in their elemental and ionic forms. Chloride is necessary in our diet, but chlorine is a deadly gas. The ionic form ends in ide. And when we’re naming ionic things, the metal always comes first and it isn’t changed. Magnesium oxide. Hydrogen chloride. Potassium iodide.

The electrons are completely handed over by the metal in the ionic bonding. It’s give and take, of the sort “you give and I take”. And the ionic formula, MgO for example, is a ratio rather than a molecular formula. In theory, ionic solids are an infinite lattice structure. They’re really brittle too, because the positive magnesium ions don’t want to get any closer to one another so pushing one ion around results in a whole heap of repercussions. There aren’t any charged particles to move around, which means there won’t be any electricity running through that block of salt I hooked up to a circuit.

But electricity flows through seawater… and what is seawater if not salt in water?

When you put an ionic solid in water, it will probably dissolve. Most ionic solids do. You’re still with me? What did I mean by dissolve, then?

When we see things dissolve, we see them disappear. But do they really dissolve? Coffee doesn’t. Coffee is a suspension, so if you leave it for long enough all the coffee grounds sink down to the bottom of the cup and are absolutely impossible (and really gross) to get out. If something is dissolved, it has had its parts viciously ripped apart and isolated by the water molecules. Water with table salt in it isn’t water and NaCl. It is water, and Na+, and Cl-. The ions are free, and what are ions if not charged particles? So salty water will transmit electricity. But coffee might not.

And if you’ve got some lonely non-metals hanging around with one another, they’ll probably form a covalent bond. There are two types of covalent bond: molecular and network. Network covalent bonds don’t really concern us right now (they’re diamond, graphite, silicon dioxide, and polymers) so let’s look closer at molecular covalent bonding.

If ionic bonding is the bully bonding, then molecular covalent is the pacifist. The atoms share electrons so they can get full shells. Awwww!

So with bromine and bromine, they get together and make Br2. (bromine, usually a gas.) How? They both have seven electrons in their outer shell. They share one electron between them so they both have eight electrons in the outer shell.

It’s a bit hard to grasp the first couple of times, so just know that group 17 (and hydrogen) have to make one bond, 16 need to make 2, 15 needs to make 3, 14 needs to make 4, and lonely little Boron only needs to make three as well.

Covalent bonding results in discrete molecules, with low melting and boiling points due to weak forces between these molecules. They also don’t conduct electricity, which is lucky! Most of our air is make up of N2, nitrogen gas (N≡N), so if it conducted electricity we’d be in a bit of trouble every thunderstorm.

Next time: Polarity. Nothing to do with Antarctica.

Now cut it in half. Cut it in half again. And again, and again, until the very small piece of cake cannot be split up anymore. It’s less than a crumb – it’s too small to see with your naked eye. That’s an atom.

Atoms were first an idea thanks to a philosopher called Democritus in Ancient Greece. Between being properly discovered and now, a very intelligent New Zealander called Ernest Rutherford succeeded in splitting the atom (early 1900s). This released a massive amount of energy, and atom-splitting reactions are the basis of nuclear fission today.

How an atom acts depends on the number of protons, with positive charge, and electrons, with negative charge, it has. An electron also has neutrons, with no charge, that change how heavy the atom is. An atom can gain or lose electrons, but it doesn’t gain or lose protons or neutrons (ok, they do, but it doesn’t concern us right now).

Why not? Protons and neutrons make up what is called the “nucleus” of an atom, which sits in the middle of an atom, while electrons zoom around the outside in specific energy levels called “shells”. Two electrons can fit in the first shell, eight in the next, then 8, 18, 18, 18…

Think of the shells like a set of Russian dolls. When the set’s all put together, you can only take off the top layer, right? It’s the same with electrons. Atoms can only lose electrons from the outermost shell to become IONS.

What I find really hard with Russian dolls is taking the first layer off. Grabbing both ends and pulling takes a lot of effort and atoms don’t like losing electrons when their outermost shell is full – well, don’t like is an understatement. It doesn’t happen.

Grab yourself a periodic table and check it out. 18 columns. 18 fit in the biggest shell… Yep, that’s how they work! It was sorted out by a chemist named Mendeleyev, according to the rules of the card game Patience or Solitaire. Group 18 are called the noble gases because they don’t react with anything. They’re perfectly happy with their full shell of electrons and don’t really want to share, thanks all the same. Group 17 are called the halogens.

So when our Russian doll has an outer layer that’s mostly complete, what do you think it would rather do: finish off the layer with one or two pieces, or lose all of its shell? That’s right; it wants to finish of the layer, in the same way a shell with only one or two electrons would rather lose them than try and gain all the electrons it needs.

Why do the atoms want to lose or gain electrons? They’re a lot more stable when their outer shell is full. And stability is the ultimate goal.

One last note: a change in the amount of neurons of an atom creates a different ISOTOPE. Carbon isotopes such as Carbon-12, carbon-13, and carbon-14 were the ones most mentioned on the TV shows I watched, such as Meet the Ancestors. They’re great. Go and watch.

Relax. Help is here, and not just for deciphering those chemical names. I don’t pretend to be an expert, but I do know my stuff, and I am good at what I do. I harbour interest in all fields of science, from the big picture of Astronomy to the small picture of Quantum Physics and everything in between.

For most people, science has been too dry for too long. If you don’t understand the amazing new discoveries, you don’t realize how unmistakably cool they are. Did you know we might be able to bring a mammoth back to life? Or how about the atoms who communicate instantaneously over instant distances? Or gene therapy? Did you not know about gene therapy?

We’ll take it slow. Let’s start with some chemistry.