Multichannel MAC protocols with a single control channel in a cognitive radio ad hoc network (CRAN) suffer from the bottleneck problem. So a multichannel MAC protocol that can realize a virtual control channel on all available channels is preferred. Discontiguous-Orthogonal Frequency Division Multiplexing (D-OFDM) enables multiple data to be sent and received on discontiguous multiple channels. In this paper, we propose a new cooperative multichannel MAC (CM-MAC) protocol using D-OFDM in a CRAN. In the proposed CM-MAC protocol, a new approach utilizing multiple discontiguous control channels is presented and a remedy to tackle new collision types by the approach using D-OFDM is provided. The proposed mechanism mitigates the bottleneck problem of the protocol using single control channel, but does not need to share hopping patterns between a sender and a receiver. In addition, cooperative communications with relays reduce the time required to send the data of low-rate secondary users (SUs) by enabling relay SUs to relay the data of source SUs. The proposed CM-MAC protocol is shown to enhance throughput. Analysis and simulations indicate that throughput performance improves compared to the MAC protocol using the split phase control channel (SPCC) approach.