Melting and boiling points* of heteroaromatic compounds

substituent

{{r}}

ring system (with position of substituent) H CH₃ C₂H₅ CO₂H CO₂C₂H₅ CONH₂ NH₂ OH OCH₃ Cl Br

benzene 80 111 136 122 212 129 184 41 154 132 156

pyridine (2) 115 129 148 137 243 107 57 107 140 170 193

pyridine (3) 115 144 165 237 224 130 65 127 179 148 173

pyridine (4) 115 145 168 315 219 156 158 148 190 147 174

pyrrole (1) 130 113 129 95 178 166 175 185** — — —

pyrrole (2) 130 148 164 208 39 174 285** — — — —

pyrrole (3) 130 143 179 148 40 152 — — — — —

furan (2) 31 65 92 133 34 142 — — 110 78 103

furan (3) 31 66 92 122 175 168 — — 110 80 103

thiophene (2) 84 113 134 129 218 180 — 218 151 128 150

thiophene (3) 84 115 136 138 208 178 146 270** 156** 136 159

pyrazole (1) 68 127 136 102 213 141 185** 72 — — —

pyrazole (3) 68 204 209 214 158 159 38 — — 40 70

pyrazole (4) 68 206 247** 275 78 — 81 118 60 77 97

isoxazole (3) 95 118 138 149 — 134 — 98 — — —

isoxazole (5) 95 122 138** 146 — 174 77 — 200** — —

imidazole (1) 90 196 208 — 218 — 315** 93 252** — —

imidazole (2) 90 144 80 164 178 312 — 251 71 165 207

imidazole (4) 90 56 76 281 157 215 — — — 117 130

pyrimidine (2) 124 138 152 197 64 166 127 180 175** 65 56

pyrimidine (4) 124 141 140 240 39 194 151 164 152 — —

pyrimidine (5) 124 153 175 270 38 212 170 210 47 37 75

pyrazine (2) 55 137 155 225*** 50 189 118 188 187 152 180

*In °C. Boldface indicates the melting points. A dash indicates that a compound is unstable or unknown or that data are not readily available.

**Calculated using the experimentally obtained boiling point at reduced pressure.

***Compound melts with decomposition.