What do the arrows in mechanisms represent?
The arrows represent the movement of a lone pair of electrons. For example, if a mechanism involves an oxygen atom forming a bond with a proton (hydrogen ion), then the oxygen would ‘donate’ a lone pair to the hydrogen ion and hence form an Oxyegn-Hydrogen bond.As electrons are negative, they are attracted to positives, and so the general rule of thumb is that the arrow starts at the negative and ends at the positive. Using our example above, oxygen is highly electronegative and so will have a strong delta - charge, and the hydrogen ion has a +1 charge, so the arrow starts at the oxygen (most negative) and ends at the hydrogen (most positive).
TK
Related Chemistry A Level answers
All answers ▸Name and draw the mechanism by which benzene reacts with ethanoyl chloride in the presence of a catalyst. Also explain why benzene undergoes a substitution reaction, rather than an addition reaction.
Aminoethane can be prepared by a reduction reaction. Identify a starting compound that can be used to prepare aminoethane by reduction, give the necessary reagent and write an equation for the reaction.
Give reasons for the increase in ionisation energy across a period in the table of elements.
You have 3.51g of hydrated zinc sulphate. You heat up the zinc sulphate until all the water has evaporated from it. The weight after heating is 1.97g. Find how many H2O molecules per zinc sulphate molecule there are in the hydrated form of it.