What are aromatic and aliphatic compounds?
Answer:
Aromatic compounds : - An aromatic compound contains a set of covalently-bound atoms with specific characteristics:
1. A delocalized conjugated π system, most commonly an arrangement of alternating single and double bonds
2. Coplanar structure, with all the contributing atoms in the same plane
3. Contributing atoms arranged in one or more rings
4. A number of π delocalized electrons that is even, but not a multiple of 4. This is known as Hückel's rule. Permissible numbers of π electrons include 2, 6, 10, 14, and so on
5. Special reactivity in organic reactions such as electrophilic aromatic substitution and nucleophilic aromatic substitution
Aliphatic compounds : - In chemistry, aliphatic compounds are organic compounds in which carbon atoms are joined together in straight or branched chains or in rings, that can be either saturated or unsaturated, but not aromatic. The simplest aliphatic compound is methane (CH4). Aliphatics include not only the fatty acids and other derivatives of paraffin hydrocarbons (alkanes), but also unsaturated compounds, including the alkenes (such as ethylene) and the alkynes (such as acetylene). The most frequently found non-carbon atoms bound to the carbon chain include hydrogen, oxygen, nitrogen, sulfur, and various halides.
In simple way aromatic compound mean ring hydrocarbon compounds
and aliphatic are straight hydrocarbon compounds
aromatic compounds have a circular benzene-derived ring structure somewhere in its makeup. Aliphatic compounds are all straight and/or branch chained.
Aliphatic compounds:
The aliphatic hydrocarbons are subdivided into three groups, homologous series according to their state of saturation: paraffins alkanes without any double or triple bonds, olefins alkenes with double bonds, which can be mono-olefins with a single double bond, di-olefins, or di-enes with two, or poly-olefins with more. The third group with a triple bond is named after the name of the shortest member of the homologue series as the acetylenes alkynes. The rest of the group is classed according to the functional groups present.
From another aspect aliphatics can be straight chain or branched chain compounds, and the degree of branching also affects characteristics, like octane number or cetane number in petroleum chemistry.
Aromatic and alicyclic compounds:
Benzene is one of the best-known aromatic compoundsCyclic compounds can, again, be saturated or unsaturated. Because of the bonding angle of carbon, the most stable configurations contain six carbon atoms, but while rings with five carbon atoms are also frequent, others are rarer. The cyclic hydrocarbons divide into alicyclics and aromatics (also called arenes).
Of the alicyclic compounds the cycloalkanes do not contain multiple bonds, whilst the cycloalkenes and the cycloalkynes do. Typically this latter type only exists in the form of large rings, called macrocycles. The simplest member of the cycloalkane family is the three-membered cyclopropane.
Aromatic hydrocarbons contain conjugated double bonds. One of the simplest examples of these is benzene, the structure of which was formulated by Kekulé who first proposed the delocalization or resonance principle for explaining its structure. For "conventional" cyclic compounds, aromaticity is conferred by the presence of 4n + 2 delocalized pi electrons, where n is an integer. Particular instability (antiaromaticity) is conferred by the presence of 4n conjugated pi electrons.
The characteristics of the cyclic hydrocarbons are again altered if heteroatoms are present, which can exist as either substituents attached externally to the ring (exocyclic) or as a member of the ring itself (endocyclic). In the case of the latter, the ring is termed a heterocycle. Pyridine and furan are examples of aromatic heterocycles while piperidine and tetrahydrofuran are the corresponding alicyclic heterocycles. The heteroatom of heterocyclic molecules is generally oxygen, sulfur, or nitrogen, with the latter being particularly common in biochemical systems.
Rings can fuse with other rings on an edge to give polycyclic compounds. The purine nucleoside bases are notable polycyclic aromatic heterocycles. Rings can also fuse on a "corner" such that one atom (almost always carbon) has two bonds going to one ring and two to another. Such compounds are termed spiro and are important in a number of natural products.
Aroma compound, a chemical compound possessing an aroma, fragrance, flavor, smell, or odor.
Aromatic compound, an organic chemical compound that contains aromatic rings (arenes) like benzene, pyridine, or indole. These compounds exhibit an unusual stability known as aromaticity, which can be understood using Hückel's rule. The term aromatic in chemistry is no longer associated with aroma, and many aromatic compounds have no smell.
In chemistry, aliphatic compounds are organic compounds in which carbon atoms are joined together in straight or branched chains or in rings, that can be either saturated or unsaturated, but not aromatic.[1] The simplest aliphatic compound is methane (CH4). Aliphatics include not only the fatty acids and other derivatives of paraffin hydrocarbons (alkanes), but also unsaturated compounds, including the alkenes (such as ethylene) and the alkynes (such as acetylene). The most frequently found non-carbon atoms bound to the carbon chain include hydrogen, oxygen, nitrogen, sulfur, and various halides.
Most aliphatic compounds have exothermic combustion reactions, thus allowing hydrocarbons such as methane to fuel Bunsen burners in the laboratory, while acetylene is used as torch fuel in pipe fitting.
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