The key difference between geminal and vicinal dihalides is that geminal dihalides have both halide groups attached to the same carbon atom whereas vicinal dihalides have their two halide groups attached to two adjacent carbon atoms in the same compound.
The terms geminal and vicinal are used with chemical compounds having substitutes. These terms distinguish compounds according to the location of substitutes compared to each other.
CONTENTS
1. Overview and Key Difference
2. What are Geminal Dihalides
3. What are Vicinal Dihalides
4. Side by Side Comparison – Geminal vs Vicinal Dihalides in Tabular Form
5. Summary
What are Geminal Dihalides?
Geminal dihalides are organic compounds containing two halide groups attached to the same carbon atom. Halides are the anions of halogen atoms. A halogen is an atom of any chemical element of the group 7 of the periodic table. When the two halide groups are attached to the same carbon atom, it makes the compound achiral at that carbon point (shows no mirror images that are non-superimposable).
Figure 01: Formation of a Geminal Dihalide
Moreover, the hybridization of this carbon atom is either sp2 or sp3 because other than the two halide groups, there can be either one or two carbon or hydrogen atoms bonded to this particular carbon atom. The geometry around this carbon centre is either trigonal planar (if the hybridization of the carbon atom is sp2) or tetrahedral (if the hybridization is sp3). The general name of geminal dihalides is alkylidene dihalide.
What are Vicinal Dihalides?
Vicinal dihalides are organic compounds having two halide groups attached to two adjacent carbon atoms of the same chemical compound. The halide group can be any of the anions formed from halogens. When the two halide groups are attached to the same carbon atom, there is a possibility for the compound to be chiral if there are no two similar groups are attached to the same carbon.
Figure 02: Formation of a Vicinal Dihalide
Moreover, hybridization of the compound around these two adjacent carbon atoms can be sp, sp2 or sp3, depending on the type of covalent bonds around them. For example, if there is a triple bond between two carbon atoms, then the compound has sp hybridization, and the geometry around the carbon atoms is linear). Similarly, if there is a double bond between these two carbon atoms bearing the halide groups, then those are sp2 hybridized carbon atoms, and the geometry around them is trigonal planar.
What is the Difference Between Geminal and Vicinal Dihalides?
The key difference between geminal and vicinal dihalides is that geminal dihalides have both halide groups attached to the same carbon atom whereas vicinal dihalides have their two halide groups attached to two adjacent carbon atoms in the same compound.
When the two halide groups are attached to the same carbon atom, it makes the compound achiral at that carbon point (shows no mirror images that are non-superimposable). When the two halide groups are attached to the same carbon atom, there is a possibility for the compound to be chiral if there are no two similar groups are attached to the same carbon.
In geminal dihalides, the hybridization of the carbon atom bearing the halide groups is either sp2 or sp3 because other than the two halide groups, there can be either one or two carbon or hydrogen atoms bonded to this particular carbon atom. In vicinal dihalides, hybridization of the compound around two adjacent carbon atoms bearing the halide groups can be sp, sp2 or sp3, depending on the type of covalent bonds around them.
Summary – Geminal vs Vicinal Dihalides
The terms geminal and vicinal are used with chemical compounds having substitutes. These terms distinguish the compounds according to the location of substitutes compared to each other. The key difference between geminal and vicinal dihalides is that geminal dihalides have both halide groups attached to the same carbon atom whereas vicinal dihalides have their two halide groups attached to two adjacent carbon atoms in the same compound.
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