Compatibility summary
You will need a travel adapter in Dominican Republic; plug types used there differ from Spain. Voltage differs by more than 20% — a voltage converter may be needed for some appliances.
Plug comparison
Spain plug types: C F
Dominican Republic plug types: A B
There is no common plug type between Spain (C F) and Dominican Republic (A B). You need a travel adapter.
Voltage comparison
Spain: 230V, 50Hz
Dominican Republic: 120V, 60Hz
Voltage converter recommended (Spain 230V vs Dominican Republic 120V).