<Tr> <Td> Picric acid </Td> <Td> 4.3 </Td> <Td> Tripropylamine </Td> <Td> 2.6 </Td> </Tr> <Tr> <Td> 2, 4 - Dinitrophenol </Td> <Td> 4.9 </Td> <Td> MTBD (7 - Methyl - triazabicyclodecene) </Td> <Td> 2.9 </Td> </Tr> <Tr> <Td> Benzoic acid </Td> <Td> 7.1 </Td> <Td> DBU (1, 8 - Diazabicycloundec - 7 - ene) </Td> <Td> 3.0 </Td> </Tr> <Tr> <Td> Phenol </Td> <Td> 8.8 </Td> <Td> TBD (Triazabicyclodecene) </Td> <Td> 3.5 </Td> </Tr>

When can resonance structures be written for molecule