  We present a study of chemistry toward 294 dense cores in 12 molecular clumps
using the data obtained from the ALMA Survey of 70 $\mu \rm m$ dark High-mass
clumps in Early Stages (ASHES). We identified 97 protostellar cores and 197
prestellar core candidates based on the detection of outflows and molecular
transitions of high upper energy levels ($E_{u}/k > 45$ K). The detection rate
of the N$_{2}$D$^{+}$ emission toward the protostellar cores is 38%, which is
higher than 9% for the prestellar cores, indicating that N$_{2}$D$^{+}$ does
not exclusively trace prestellar cores. The detection rates of the DCO$^{+}$
emission are 35% for the prestellar cores and 49% for the protostellar cores,
which are higher than those of N$_{2}$D$^{+}$, implying that DCO$^{+}$ appears
more frequently than N$_{2}$D$^{+}$ in both prestellar and protostellar cores.
Both N$_{2}$D$^{+}$ and DCO$^{+}$ abundances appear to decrease from the
prestellar to protostellar stage. The DCN, C$_{2}$D and $^{13}$CS emission
lines are rarely seen in the dense cores of early evolutionary phases. The
detection rate of the H$_{2}$CO emission toward dense cores is 52%, three times
higher than that of CH$_{3}$OH (17%). In addition, the H$_{2}$CO detection
rate, abundance, line intensities, and line widths increase with the core
evolutionary status, suggesting that the H$_{2}$CO line emission is sensitive
to protostellar activity.
