Arrange the four groups attached to the central alpha carbon of alanine in order of decreasing Cahn-Ingold-Prelog (CIP) priority (from highest priority to lowest priority).

### The order 1. **Alpha carbon**: it is the central atom in the standard amino-acid structure. 2. **Amino group**: it is one of the groups attached to the alpha carbon. 3. **Carboxyl group**: it is another group attached to the same central carbon. 4. **Hydrogen**: this is also attached to the alpha carbon. 5. **R group**: the variable side chain completes the set of four attachments. The last four items are all attached directly to the alpha carbon; they are not a chain radiating from one another. ### Terms - **Carboxyl group**: a carbon-containing acidic functional group, written –COOH.