Table 1. Overview of Thermochemical and Structural Investigations of M, C, D and Their HCl Salts^a.

compd	anhydrates		hydrates
Morphine (M)	M-I°	M-II	M-1H
Kofler and Kofler28−30	mp 240 °Cb (dec.c)	mp 197 °C	existence of a hydrate
Kuhnert-Brandstaetter31	mp 245–255 °C	mp 197 °C	dehy.d 115–140 °C
CSD Refcode family34	Guguta et al.35,e		MORPHM37,38
	MORPIN0136		MORPIN39,f
Codeine (C)	C-I°		C-1H
Kofler and Kofler29,30	mp 155 °C		mp 62–68 °C
Kuhnert-Brandstaetter31	mp 156 °C		dehy.d
CSD Refcode family34	ZZZTSE40−43		ZZZTZQ (unit cell)40
			ZZZTZQ 01(without H)42
Ethylmorphine (D)	D-I°		D-1H
Kuhnert-Brandstaetter31	Sluggish melting, softening
Morphine HCl (MCl)	MCl-I°	MCl-II	MCl-3H
Kofler and Kofler29,30	mp > 300 °C  (dec.c)		trihydrate
Lindpainter32	mp 295–300 °C	mp 280–284 °C
Kuhnert-Brandstaetter31	mp 285–320 °C		dehy.d at 80 °C
CSD Refcode family34	Guguta et al.35,e		MORPHC45
	EFASAH44
Codeine HCl (CCl)	CCl-I°		CCl-2H
Kuhnert-Brandstaetter31	280–292 °C (dec.c)		partial melting at 165–170 °C
			inhom. melting 140–160 °Cg
Kuhnert-Brandstaetter33	290 °C (N2 purge)		mp 140–150 °C (hom.i)
CSD Refcode family34	ZZZRFQ46,h
Ethylmorphine HCl (DCl)	DCl-I		DCl-2H
Kuhnert-Brandstaetter31	170–174 °C		148–155 °C (viscous melt)
Kuhnert-Brandstaetter33			mp 122–125 °C

^aAnhydrate forms are denoted with roman numerals and hydrates according to stoichiometry, e.g., 2H indicates a dihydrate (see also section 1 of the Supporting Information).

^bThe same phase exhibits different morphologies.

^cdec: decomposition.

^ddehy: dehydration.

^eStructure solved from PXRD data, not in the Cambridge Structural Database (CSD³⁴).

^fUnit cell parameters reported for anhydrous morphine correspond to those of the monohydrate, as previously noted by Guguta et al.³⁵

^ginhom: inhomogeneous, the authors have corrected the dihdyrate melting point to 140–160 °C.³³ In earlier publications, liquefication of the compound was incorrectly described as the melting event of the hydrate^31,47

^hNo atomic coordinates.

ⁱhom: homogeneous.