Question

Following compounds are related as: (A) Geometrical isomers (B) Metamers (C) Position isomers (D) Functional isomers

Short answer

The type of relationship between chemical compounds can be identified easily by following these steps: 1. Identify the molecular formula: If the compounds provided do not share the same molecular formula, they are not isomers. 2. Examine the functional groups: If the molecular formulas are the same, but functional groups are different, they are Functional Isomers. 3. Analyze the spatial arrangement of atoms: If compounds have different spatial arrangement but same connectivity of atoms and functional groups, they are Geometrical Isomers. 4. Analyze the distribution of carbon atoms: If compounds have same spatial arrangement and functional group, but differ in the distribution of carbon atoms around the functional group, they are Metamers. 5. Analyze the position of functional groups: If the compounds still have the same molecular formula and functional groups but the functional group is at different positions on the carbon chain, they are Position Isomers. Follow these steps in order to accurately classify the compounds.

Step-by-step solution

Identify the molecular formula of the compounds

Examine the molecular formulas of the given compounds to see if they are the same. If they are not, then these compounds cannot be isomers of any kind.

Examine the functional groups

If the molecular formulas are identical, look at the functional groups of each compound. If the functional groups are different, then the compounds are Functional Isomers. If they are the same, proceed to the next step.

Analyze the arrangement of atoms

Look at the spatial arrangement of atoms in the compounds. If the arrangement is different but the connectivity of atoms and functional groups is the same, then these are Geometrical Isomers.

Analyze the distribution of carbon atoms around the functional group

In the case that the functional group is the same and the spatial arrangement of atoms is identical, check the distribution of carbon atoms around the functional group. If the carbon atoms are distributed differently around the functional group, then the compounds are Metamers.

Analyze the position of functional groups in compounds

If none of the above conditions apply and yet the compounds still have the same molecular formula and functional groups then check the position of the functional group on the carbon chain. If the functional group is located at different positions on the carbon chain in the compounds, then they are Position Isomers. Note: These steps should be carried out in the order mentioned to accurately classify the compounds.

Key concepts

Geometrical Isomers

Understanding geometrical isomers starts with recognizing the rigidity within a molecule that prevents it from rotating freely. These isomers are also known as cis-trans isomers, where similar atoms or groups are positioned differently around an inflexible structure, such as a double bond or a ring. To visualize this, imagine two road signs on opposite sides of a pole; one cannot simply be flipped or rotated to overlay the other without physically moving it around the pole.

For example, consider two compounds with the formula C₂H₂Cl₂. One structure has both chlorine atoms on the same side of the double bond (cis), while the other has them on opposite sides (trans). Even though they share the same formula, their spatial arrangements drastically affect their physical and chemical properties, such as solubility and boiling points. Geometrical isomers are crucial in biological systems where the shape of a molecule can determine its function.

Functional Isomers

Functional isomers are fascinating because they're like twins with different personalities. They have the same molecular formula but differ in the type of functional group present. Functional groups are distinctive arrangements of atoms that largely dictate the behavior of molecules during chemical reactions. For instance, alcohols and ethers can have the same number of carbons, hydrogens, and an oxygen atom; however, where alcohols have a -OH group, ethers will have an -O- linkage.

Take C₂H₆O; it could be ethanol (an alcohol) or dimethyl ether (an ether). Even though they share the same formula, the -OH group in ethanol gives it quite different properties compared to the ether linkage in dimethyl ether, affecting its reactivity, boiling point, and how it interacts with other molecules. This type of isomerism emphasizes that structure strongly influences function.

Metamers

Metamers are a riddle wrapped in a molecule. In metamers, the molecules have the same functional group but differ in how the carbon atoms are distributed on either side of this group. Essentially, the carbon skeleton is divided differently on each side of a functional group such as –O–, –S–, or –NH–.

Consider the ethers C₄H₁₀O. One could be butyl methyl ether with a butyl group on one side of the oxygen and a methyl group on the other, whereas another could be ethyl propyl ether, with an ethyl and propyl group flanking the oxygen. The functional group, an ether linkage in this case, is the same; however, the different arrangement of carbon chains bestows these metamers with unique physical and chemical properties. Such isomerism is particularly important in pharmaceuticals, where the arrangement of atoms can influence the drug's effectiveness.

Position Isomers

Last but not least, position isomers are molecules playing musical chairs with their functional groups. Here, the molecular formula remains constant, and the functional groups are identical, but their location on the carbon chain is different. Picture a necklace with a charm; shifting the charm to different positions along the chain illustrates position isomerism.

An example includes pentanols with the formula C₅H₁₂O. In one isomer, the -OH group (alcohol) might be on the first carbon (1-pentanol), while another isomer may have it on the second carbon (2-pentanol). Different positions of these functional groups impact boiling points, solubility, and how the molecule might react in a given situation. Recognizing position isomers is instrumental in organic synthesis and understanding biochemical pathways within living organisms.