Andrew

Because of the lack of leaving group on these carbonyls (the leaving group would have to be an alkyl group leaving as a carbanion – not generally very stable), they react differently to the general reactions discussed on the previous page. The C=O bond is still polar and attractive to nucleophiles however, so they can attack here. However, it is important … Read more

A carbonyl is a molecule containing the C=O functional group. For the purposes of this chapter they will be split into 2 categories – one category will be ketones and aldehydes, the other will include pretty much everything else. To see how this breaks down; Of the latter class a couple of examples have been given – some other important carbonyls … Read more

The three types of hybrid orbitals we have seen are sp, sp2 and sp3. Hybrid Type Angle between orbitals Arrangement Example C-C Bond Strength (kJ mol-1) C-C Bond Length (Å) sp3 109° 28′ Tetrahedral Ethane (C2H6) 376 1.54 sp2 120° Trigonal planar Ethene (C2H4) 611 1.33 sp 180° Linear Ethyne (C2H2) 835 1.20 As you might … Read more

The third type of hybridisation commonly encountered in organic chemistry is sp.  By extrapolation, it is obvious that this involves the use of one s orbital, and one p orbital.  Let us have a look at an sp hybridised carbon atom: In this diagram, there are two unhybridised p orbitals, and two sp orbitals.  The sp orbitals … Read more

Atoms bond together because in doing so, they can achieve a lower overall energy.  In simple terms, making bonds releases energy, and breaking bonds requires energy. The bonds we most often come across in organic chemistry are covalent bonds.  These are bonds where electron pairs are shared between atoms, usually with one electron from each pair … Read more

We now know what the orbitals of a general atom look like, but now we need to know in what order the orbitals are filled on progressing through the periodic table, so we can then make predictions about those elements. The following rules can be used to predict the lowest energy state of the electronic configuration (the ground state): … Read more

We now know, from our previous discussion, that the electrons orbit the nucleus at a very large distance (on a nuclear scale),  but what is the nature of the “path” they follow? An electron orbiting a nucleus is described by a wavefunction. This is contrary to the common image of electrons being like little balls orbiting … Read more

Before we start to discuss more complicated areas of chemistry, it is necessary to ensure that certain concepts of atomic structure are understood. Firstly, the atom is composed of a nucleus (about 10-15m in diameter) at the centre which contains most of the mass of the atom, and orbiting electrons (negatively charged particles), which have negligible mass.  The nucleus … Read more

The aromatic ring is a very stable and electron rich entity – the delocalised π electrons lie above and below the plane of the ring and make it more attractive to electrophiles than nucleophiles. Substitution is likely to be the mechanism because this will return the aromaticity to the ring which is energetically favourable. However, because benzene itself is so stabilised … Read more

Unsaturated hydrocarbons with a triple bond are known as alkynes or acetylenes. e.g. ethyne: The naming of alkynes follows the same rules we used for alkanes and alkenes earlier.  i.e. ethyne (shown above), propyne etc. Ethyne is the most commonly encountered member of this group.  It can be prepared by the following method: This process of addition of water to calcium carbide is used industrially.  Other mechanisms … Read more