virtualbox – Creating cd-rom ISO image with dd

I have created a script to build images for floppy and cdrom with dd.
These images is for use with a virtual machine on VirtualBox, with MS-DOS system installed.

dd if=/dev/zero of=floppy.img bs=1k count=1440  
sudo losetup /dev/loop0 floppy.img  
sudo mkfs -t vfat /dev/loop0  
sudo losetup -d /dev/loop0  
sudo mount floppy.img /media/floppy  
sudo rm -rf /media/floppy/{*,.*}  
sudo rm -rf /media/floppy/*  
sudo cp -R /home/jonas/'VirtualBox VMs'/floppy/* /media/floppy/  
sudo umount /media/floppy

dd if=/dev/zero of=cdrom.iso bs=1M count=699  
sudo losetup /dev/loop1 cdrom.iso  
sudo mkfs -t vfat /dev/loop1  
sudo losetup -d /dev/loop1  
sudo mount iso9660 cdrom.iso /media/cdrom  
sudo rm -rf /media/cdrom/{*,.*}  
sudo rm -rf /media/cdrom/*  
sudo cp -R /home/jonas/'VirtualBox VMs'/cdrom/* /media/cdrom/  
sudo umount /media/cdrom

The floppy image runs well on virtual machine, but the iso image created for emulating cdrom not.

When I change drive to D: in MS-DOS, the following message is shown:

CDR103: CDROM not High Sierra or ISO-9660 format reading drive D.

Can anyone help-me?

Thanks.