$(a)$ Heated : it is charred
$(b)$ $I_2$ solution : no violet colour
$(c)$ Fehling solution : reddish brown ppt. is observed
$(d)$ It does not reduce copper$(II)$ acetate to $Cu_2O$ . No red precipiated is observed in $5/ min$
The carboxylate which satisfy all the above observation


| Peptide | $R _1$ | $R _2$ |
| $I$ | $H$ | $H$ |
| $II$ | $H$ | $CH _3$ |
| $III$ | $CH _2 COOH$ | $H$ |
| $IV$ | $CH _2 CONH _2$ | $( CH _2)_4 NH _2$ |
| $V$ | $CH _2 CONH _2$ | $CH _2 CONH _2$ |
| $VI$ | $( CH _2)_4 NH _2$ | $( CH _2)_4 NH _2$ |
| $VII$ | $CH _2 COOH$ | $CH _2 CONH _2$ |
| $VIII$ | $CH _2 OH$ | $( CH _2)_4 NH _2$ |
| $IX$ | $( CH _2)_4 NH _2$ | $CH _3$ |
