Final answer:
Compounds that cannot exist in cis and trans forms include but-2-enoic acid. Geometric isomerism, also known as cis-trans isomerism, is observed in compounds with a double bond. Cis trans isomerism is important in biological systems, particularly in fatty acids.
Step-by-step explanation:
Compounds that Cannot Exist in Cis and Trans Forms
Compounds that have a rigid structure in their molecule and fail certain rules cannot exist in cis and trans forms. One example of such a compound is but-2-enoic acid, which has two hydrogen atoms on one of its doubly bonded carbon atoms. This violates a rule and prevents it from existing as cis and trans isomers.
Geometric Isomerism
Geometric isomerism, also known as cis-trans isomerism, is a type of isomerism observed in compounds with a double bond. In this type of isomerism, the order of atom bonding remains the same, but the arrangement of atoms in space differs. Alkenes and cyclic compounds can exhibit cis-trans isomerism.
Role of Cis Trans Isomerism in Biological Systems
Cis trans isomerism plays a vital role in biological systems, particularly in fatty acids. Fatty acids, which are significant components of fats and vegetable oils, often contain double bonds in the cis configuration. For example, oleic acid, a fatty acid with one cis double bond, is found in vegetable oils. Linoleic acid, with two cis double bonds, is another example of a fatty acid that exhibits cis-trans isomerism.