Final answer:
During the partial hydrogenation of commercial vegetable oils, unsaturated bonds are converted into trans-C=C bonds that are undesirable.
Step-by-step explanation:
During the partial hydrogenation of commercial vegetable oils, unsaturated bonds are converted into trans-C=C bonds that are undesirable. These trans-C=C bonds are formed when some of the cis-C=C bonds are converted during the process. Trans-fatty acids, which contain trans-C=C bonds, are known to have negative impacts on health.