Melting (in bold) and boiling points (C) of heteroaromatic compounds

▪ Table

Melting and boiling points* of heteroaromatic compounds

substituent

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.

See as table:

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