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A Carbanion Is an Anion in Which Carbon Has an Unshared Pair Of

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A Carbanion Is an Anion in Which Carbon Has an Unshared Pair Of A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons.[1] The carbanion exists in a trigonal pyramidal geometry. Formally a carbanion is the conjugate base of a carbon acid. − − R3C-H + B → R3C + H-B where B stands for the base. A carbanion is one of several reactive intermediates in organic chemistry. Definitions A carbocation was previously often called a carbonium ion but questions arose on the exact meaning.[1] In present day chemistry a carbocation is any positively charged carbon atom. Two special types have been suggested: carbenium ions (protonated carbenes, hence the name) are trivalent and carbonium ions (protonated alkanes) are pentavalent or hexavalent. University level textbooks only discuss carbocations as if they are carbenium ions,[2] or discuss carbocations with a fleeting reference to the older phrase of carbonium ion[3] or carbenium and carbonium ions.[4] One textbook to this day clings on to the older name of carbonium ion for carbenium ion and reserves the phrase hypervalent carbenium + [5] ion for CH5 . Carbonium ion of methane Radical (chemistry) From Wikipedia, the free encyclopedia Jump to: navigation, search "Free radical" redirects here. For other uses, see Free radical (disambiguation). Moses Gomberg (1866-1947), the founder of radical chemistry Radicals (often referred to as free radicals) are atoms, molecules, or ions with unpaired electrons or an open shell configuration. Free radicals may have positive, negative, or zero charge. With some exceptions, these unpaired electrons cause radicals to be highly chemically reactive. Free radicals play an important role in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes. In living organisms, superoxide and nitric oxide and their reaction products regulate many processes, such as control of vascular tone and thus blood pressure. They also play a key role in the intermediary metabolism of various biological compounds. Such radicals can even be messengers in a phenomenon dubbed redox signaling. A radical may be trapped within a solvent cage or be otherwise bound. Inductive effect From Wikipedia, the free encyclopedia Jump to: navigation, search This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: "Prose is incoherent, probably needs an expert". Please help improve this article if you can. (July 2012) In chemistry and physics, the inductive effect is an experimentally observable effect of the transmission of charge through a chain of atoms in a molecule by electrostatic induction.[1] The net polar effect exerted by a substituent is a combination of this inductive effect and the mesomeric effect. The electron cloud in a σ-bond between two unlike atoms is not uniform and is slightly displaced towards the more electronegative of the two atoms. This causes a permanent state of bond polarization, where the more electronegative atom has a slight negative charge (δ–) and the other atom has a slight positive charge (δ+). If the electronegative atom is then joined to a chain of atoms, usually carbon, the positive charge is relayed to the other atoms in the chain. This is the electron-withdrawing inductive effect, also known as the effect. Some groups, such as the alkyl group are less electron-withdrawing than hydrogen and are therefore considered as electron-releasing. This is electron releasing character and is indicated by the effect. In short alkyl groups are tending to give electrons leading to induction effect. As the induced change in polarity is less than the original polarity, the inductive effect rapidly dies out, and is significant only over a short distance. The inductive effect is permanent but feeble, as it involves the shift of strongly held σ-bond electrons, and other stronger factors may overshadow this effect. The inductive effect may be caused by some molecules also. Relative inductive effects have been experimentally measured with reference to hydrogen: Inductive effects can be measured through the Hammett equation. The inductive effect can also be used to determine whether a molecule is stable or unstable depending on the charge present on the atom under consideration and the type of groups bonded to it. For example, if an atom has a positive charge and is attached to a −I group its charge becomes 'amplified' and the molecule becomes more unstable than if I- effect was not taken into consideration. Similarly, if an atom has a negative charge and is attached to a +I group its charge becomes 'amplified' and the molecule becomes more unstable than if I-effect was not taken into consideration. But, contrary to the above two cases, if an atom has a negative charge and is attached to a −I group its charge becomes 'de-amplified' and the molecule becomes more stable than if I-effect was not taken into consideration. Similarly, if an atom has a positive charge and is attached to a +I group its charge becomes 'de-amplified' and the molecule becomes more stable than if I-effect was not taken into consideration. The explanation for the above is given by the fact that more charge on an atom decreases stability and less charge on an atom increases stability. The inductive effect also plays a vital role in deciding the acidity and basicity of a molecule. Groups having +I effect attached to a molecule increases the overall electron density on the molecule and the molecule is able to donate electrons, making it basic. Similarly groups having -I effect attached to a molecule decreases the overall electron density on the molecule making it electron deficient which results in its acidity. As the number of -I groups attached to a molecule increases, its acidity increases; as the number of +I groups on a molecule increases, its basicity increases. Hyperconjugation From Wikipedia, the free encyclopedia Jump to: navigation, search In organic chemistry, hyperconjugation is the interaction of the electrons in a sigma bond (usually C–H or C–C) with an adjacent empty (or partially filled) non-bonding p- orbital, antibonding π orbital, or filled π orbital, to give an extended molecular orbital that increases the stability of the system.[1][2] Only electrons in bonds that are β to the positively charged carbon can stabilize a carbocation by hyperconjugation. .
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