Which one of the following carbon compounds will not give a sooty flame ?

The tendency of a hydrocarbon to produce a sooty flame depends on its degree of saturation and carbon-to-hydrogen ratio. Saturated hydrocarbons, such as alkanes, generally undergo more complete combustion and produce a clean, blue flame [1]. Hexane (C6H14) is a saturated aliphatic hydrocarbon (alkane) and thus will not give a sooty flame under normal oxygen-rich conditions [1]. In contrast, unsaturated carbon compounds, particularly aromatic hydrocarbons, have a high carbon-to-hydrogen ratio and typically undergo incomplete combustion, resulting in a yellow flame with significant black smoke or soot [3]. Benzene, naphthalene, and anthracene are all aromatic hydrocarbons with cyclic structures that act as soot precursors . Single-ring aromatics like benzene have much greater sooting tendencies than alkanes like hexane because they can grow directly into larger polycyclic aromatic hydrocarbons (PAHs) and soot particles .

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Activity 4.4 > p. 69
2. [3] https://downloads.regulations.gov/EPA-HQ-OAR-2022-0829-0435/attachment_9.pdf