p-Cymenesulphonic acid: An organic acid synthesised from citrus waste

An organic acid, p-cymene-2-sulphonic acid, is synthesised from citrus waste and demonstrated to be comparable to p-toluenesulphonic acid in examples of acid catalysis. Firstly the essential oil found in citrus waste is extracted by either steam distillation or microwave irradiation. Oxidising the limonene in the citrus oil to p-cymene followed by sulphonation gives p-cymene-2-sulphonic acid.

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► Limonene was converted to p-cymene.
► Sulphonation of p-cymene gave p-cymene-2-sulphonic acid (p-CSA).
► p-CSA is demonstrated as being a good acid catalyst.
► Hence citrus waste was valourised into a sulphonic acid.