fuck explaining like im 5 explain like im the dumbest 2 year old youve ever met. every explanation ive read (even on this sub) doesnt make sense. neither does the hand example
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Chiral molecules are ones that are mirror images of each other, but no matter how you rotate them they don’t have the same shape. Imagine the two halves of someone’s face. They’re made up of the same features, but no change in orientation can make the left side of your face into the right side of your face. Achiral molecules are shapes that can be oriented into the original shape after being mirrored, like a cube, pyramid, or sphere (not that achiral molecules are only simple shapes.
Your hands are chiral. You can rotate them however you want, but you’ll never get your thumbs and palms pointed in the same direction at the same time.
Two forks are achiral. You can place them next to each other and they’ll be identical, with all their bits facing the same directions. This is possible because forks have at least one axis of symmetry, which is what makes them achiral.
Have a look at the letters p and d:
You can rotate the p to turn it into a d. If you wanted to make a set of magnetic fridge letters, you wouldn’t need to separately make p’s and d’s, you could just make extra p’s.
Have a look at b and d:
No matter how you rotate b, you can’t turn it into d. You’d have to flip it over, which is cheating for a fridge magnet.
So b and d and p and q all have kind of the “same” shape, but not really – you have to make the shape AND its mirror image, because the shape is not the same as its mirror image.
the shape of these letters is “chiral”. It’s not the same as its mirror image.
Similarly, n and u are (the same) chiral shape. We don’t have any *use* for the mirror image, but nonetheless, it’s not the same as its mirror image. If you want to make some “n” fridge magnets, you have to be careful not to make the mirror image my mistake.
However, the letters v, w and c are *not* chiral: each of these is the same as its mirror image – as in, if you make a “mirror image” c by mistake, it’s okay, you just rotate it upside-down on the fridge and find that the “mirror” c is exactly the same shape as the “original” c.
That’s two dimensions, but in 3D, there’s the same idea. Shapes might, or might not, be the “same” as their mirror images. A chair is not chiral: a mirror image chair is the same shape as the original chair. But a computer keyboard is chiral – if someone gave you a “mirror image” keyboard, you’d send it back and ask for a “proper” one.
Some molecules come turn out to be not the same as their mirror images. Then, instead of one molecule, there are actually two with the same chemical formula, but the structures are mirror images.
They’ll have (in their pure form) the same melting point, boiling point, colour, crystal structure etc – but they’ll react differently with other chiral molecules. Since almost every organic molecule in our bodies is chiral, that can make a big difference to (for example) how effective a molecule is as medecine or nutrition.
Chiral means “handed”. As in, two shapes which are “the same”, but mirror-images – like your hands, or left and right shoes. All the parts are connected the same, but however you try, you can’t turn them around so that they aren’t mirror images any more.
Molecules can be like that. Let’s build one.
Imagine a tetrahedral die (a d4, if you ever played D&D or similar – we’ll get to molecules in a moment). Label the four corners 1, 2, 3 and 4. Put it on the table with the 1 at the top, and look down at the other three corners. Depending on where you put the numbers, the 2, 3, 4 could go clockwise, or they could go anticlockwise – and they’re different, like your shoes. There’s no way to move the die around and make them go the other way. The two arrangements are mirror-images; the die is “chiral”.
OK, now a real molecule. CClFlBrI. One carbon atom in the middle, its bonds forming a tetrahedron. Four other, different atoms (chlorine, fluorine, bromine, iodine) on the bonds, “labelling” the corners. Except now, instead of 1, 2, 3, 4, the labels are CL, Fl, Br, I. Look down from, say, the CL, and the sequence Fl, Br, I could run either clockwise or anticlockwise. The two shapes are mirror images, and you can’t turn one into the other by just turning it around. The molecule is chiral, just like the die.
You can add more complex arrangements of atoms (a hydroxyl group, a longer hydrocarbon chain, whatever takes your fancy) in place of the single atoms; the principle will stay the same. As long as the structures at the four corners are all different, there will be mirror image shapes. That’s chirality, basically.
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