Molecular formula, compound exact mass, HRESI [M + H]⁺ and acylium ions (RCO⁺) observed in MS/MS spectra of amides^a.

Amides	Molecular formula	[M + H]+ calculated	[M + H]+ observed	Error ppm	RCO+	Molecular formula
1a	C17H19NO5	318.1336	318.1337	0.31	221.0803	C12H13O4+
1b	C16H19NO5	306.1336	306.1345	2.94	221.0859	C12H13O4+
1c	C20H31NO4	350.2326	350.2334	2.28	221.0817	C12H13O4+
1d	C17H25NO4	308.1856	308.1859	0.97	221.0830	C12H13O4+
1e	C16H21NO5	308.1492	308.1496	1.30	221.0822	C12H13O4+
1f	C17H23NO4	306.1700	306.1704	1.31	221.0815	C12H13O4+
2a	C19H29NO3	320.2220	320.2226	1.87	191.0703	C11H11O3+
2b	C16H23NO3	278.1751	278.1758	2.52	191.0702	C11H11O3+
2c	C15H19NO4	278.1387	278.1389	0.72	191.0706	C11H11O3+
2d	C16H21NO3	276.1594	276.1602	2.90	191.0700	C11H11O3+
2e	C15H17NO4	276.1230	276.1235	1.81	191.0702	C11H11O3+
3a	C13H14BrNO2	296.0281	296.0282	0.34	208.9588	C9H6BrO+
3b	C14H18BrNO	296.0645	296.0647	0.68	208.9585	C9H6BrO+
3c	C17H24BrNO	338.1114	338.1116	0.59	208.9533	C9H6BrO+
4a	C14H15NO4	262.1074	262.1072	−0.76	175.0384	C10H7O3+
4b	C18H25NO3	304.1907	304.1902	−1.64	175.0380	C10H7O3+
5a	C17H25NO	260.2008	260.2010	0.77	131.0430	C9H7O+
5b	C14H19NO	218.1539	218.1538	−0.46	131.0487	C9H7O+
5c	C13H15NO2	218.1175	218.1180	2.29	131.0482	C9H7O+
5d	C13H13NO2	216.1019	216.1015	−1.85	131.0480	C9H7O+
6a	C17H19NO3	286.1438	286.1441	1.05	201.0556	C12H10O3+
6b	C17H21NO3	288.1594	288.1596	0.69	201.0535	C12H10O3+
7a	C17H23NO3	274.1802	274.1800	−0.73	187.0744	C12H12O2+
7b	C20H29NO2	316.2260	316.2258	−0.63	187.0743	C12H12O2+
7c	C17H21NO2	272.1645	272.1646	0.37	187.0744	C12H12O2+
8a	C16H20BrNO	322.0801	322.0801	0.00	234.9745	C11H9BrO+
8b	C16H18BrNO	320.0645	320.0649	1.25	234.9749	C11H9BrO+
9	C17H23NO5	322.1649	322.1649	0.00	223.0969	C12H15O4+
10	C17H23NO3	290.1751	290.1752	0.34	205.0845	C12H14O3+

^aRCO⁺ = [[M + H] − NR_dR_e].