Determine whether each structure is likely to be colored or not. For those that you predict to be colored, indicate the extended conjugation by marking the series of continuous sp² hybridized atoms.
(d)
(e)
(f)

Verified step by step guidance

1. Step 1: Analyze the structures provided in the image. For a compound to be colored, it typically needs an extended conjugation system (a series of alternating single and double bonds) and the ability to absorb visible light. This is often associated with π-electron delocalization over a large portion of the molecule.
2. Step 2: For structure (i), observe the presence of an azo group (-N=N-) connecting two aromatic rings. Azo compounds are often colored due to their extended conjugation system. Mark the continuous sp2 hybridized atoms starting from one aromatic ring, through the azo group, and into the second aromatic ring.
3. Step 3: For structure (ii), note the presence of a fused aromatic system (chromophore) and substituents like methoxy (-OCH3) and dimethylamino (-N(CH3)2) groups. These groups can act as auxochromes, enhancing the molecule's ability to absorb visible light. Mark the extended conjugation system across the fused aromatic rings and the carbonyl group.
4. Step 4: For structure (iii), examine the aromatic rings and the ketone group. While there is conjugation within the individual aromatic rings, the conjugation does not extend across the entire molecule due to the lack of connectivity between the rings. This structure is less likely to be colored.
5. Step 5: Summarize the findings: (i) and (ii) are likely to be colored due to their extended conjugation systems, while (iii) is less likely to be colored. Ensure the extended conjugation is marked appropriately for (i) and (ii).

Key Concepts

Conjugation

Conjugation refers to the overlap of p-orbitals across adjacent sp2 hybridized atoms, allowing for the delocalization of π electrons. This delocalization stabilizes the molecule and can lead to color in organic compounds, as it lowers the energy gap between electronic states, allowing for visible light absorption.

Color in Organic Compounds

The color of organic compounds is often due to the presence of conjugated systems, where the extended π-electron system can absorb specific wavelengths of light. Compounds with longer conjugated systems typically absorb light in the visible spectrum, resulting in color, while those with shorter systems may appear colorless.

Hybridization and Molecular Geometry

Hybridization describes the mixing of atomic orbitals to form new hybrid orbitals, which influences the geometry and bonding of molecules. In organic chemistry, sp2 hybridization is common in alkenes and aromatic compounds, leading to planar structures that facilitate conjugation and affect the compound's electronic properties.