In organic chemistry, an alkene is an unsaturated hydrocarbon that contains a carbon–carbon double bond. The words alkene and olefin are used interchangeably. Acyclic alkenes, with only one double bond and no other functional groups, known as mono-enes, form a homologous series of hydrocarbons with the general formula CnH2n. Alkenes have two hydrogen atoms fewer than the corresponding alkane; the simplest alkene, with the IUPAC name ethene, is the organic compound produced on the largest scale industrially. Aromatic compounds are drawn as cyclic alkenes, but their structure and properties are different and they are not considered to be alkenes. Like a single covalent bond, double bonds can be described in terms of overlapping atomic orbitals, except that, unlike a single bond, a carbon–carbon double bond consists of one sigma bond and one pi bond; this double bond is stronger than a single covalent bond and shorter, with an average bond length of 1.33 ångströms. Each carbon of the double bond uses its three sp2 hybrid orbitals to form sigma bonds to three atoms.
The unhybridized 2p atomic orbitals, which lie perpendicular to the plane created by the axes of the three sp² hybrid orbitals, combine to form the pi bond. This bond lies outside the main C–C axis, with half of the bond on one side of the molecule and half on the other. With a strength of 65 kcal/mol, the pi bond is weaker than the sigma bond. Rotation about the carbon–carbon double bond is restricted because it incurs an energetic cost to break the alignment of the p orbitals on the two carbon atoms; as a consequence, substituted alkenes may exist as one of called cis or trans isomers. More complex alkenes may be named with the E–Z notation for molecules with three or four different substituents. For example, of the isomers of butene, the two methyl groups of -but-2-ene appear on the same side of the double bond, in -but-2-ene the methyl groups appear on opposite sides; these two isomers of butene are different in their chemical and physical properties. Twisting to a 90° dihedral angle between two of the groups on the carbons requires less energy than the strength of a pi bond, the bond still holds.
The carbons of the double bond become pyramidal, which allows preserving some p orbital alignment—and hence pi bonding. The other two attached; this contradicts a common textbook assertion that the two carbons retain their planar nature when twisting, in which case the p orbitals would rotate enough away from each other to be unable to sustain a pi bond. In a 90°-twisted alkene, the p orbitals are only misaligned by 42° and the strain energy is only around 40 kcal/mol. In contrast, a broken pi bond has an energetic cost of around 65 kcal/mol; some pyramidal alkenes are stable. For example, trans-cyclooctene is a stable strained alkene and the orbital misalignment is only 19°, despite having a significant dihedral angle of 137° and a degree of pyramidalization of 18°. Trans-cycloheptene is stable at low temperatures; as predicted by the VSEPR model of electron pair repulsion, the molecular geometry of alkenes includes bond angles about each carbon in a double bond of about 120°. The angle may vary because of steric strain introduced by nonbonded interactions between functional groups attached to the carbons of the double bond.
For example, the C–C–C bond angle in propylene is 123.9°. For bridged alkenes, Bredt's rule states that a double bond cannot occur at the bridgehead of a bridged ring system unless the rings are large enough. Following Fawcett and defining S as the total number of non-bridgehead atoms in the rings, bicyclic systems require S ≥ 7 for stability and tricyclic systems require S ≥ 11. Many of the physical properties of alkenes and alkanes are similar: they are colourless and combustable; the physical state depends on molecular mass: like the corresponding saturated hydrocarbons, the simplest alkenes, ethene and butene are gases at room temperature. Linear alkenes of five to sixteen carbons are liquids, higher alkenes are waxy solids; the melting point of the solids increases with increase in molecular mass. Alkenes have stronger smells than the corresponding alkane. Ethylene is described to have a "sweet" odor, for example; the binding of cupric ion to the olefin in the mammalian olfactory receptor MOR244-3 is implicated in the smell of alkenes.
Strained alkenes, in particular, like norbornene and trans-cyclooctene are known to have strong, unpleasant odors, a fact consistent with the stronger π complexes they form with metal ions including copper. Alkenes are stable compounds, but are more reactive than alkanes, either because of the reactivity of the carbon–carbon pi-bond or the presence of allylic CH centers. Most reactions of alkenes involve additions to this pi bond. Alkenes serve as a feedstock for the petrochemical industry because they can participate in a wide variety of reactions, prominently polymerization and alkylation. Alkenes react in many addition reactions. Most of these addition reactions follow the mechanism of electrophilic addition. Examples are hydrohalogenation, halohydrin format
Lalji Tandon is an Indian politician serving as the 22nd and current Governor of Madhya Pradesh. He is a protégé of Atal Bihari Vajpayee. Tandon was born in Chowk village in Lucknow, United Provinces, British India to Shivnarayan Tandon and Annpurna Devi, he graduated from Kalicharan Degree College. Tandon married Krishna Tandon on 26 February 1958, with, he has been a member of Uttar Pradesh Vidhan Parishad for two terms, 1978–84 and remained the Leader of House, of the Council, 1990–96. Subsequently he remained a member of Legislative Assembly for three terms, 1996–2009, remained the Leader of Opposition in the Assembly, 2003-07, he had served as Urban Development minister in the Uttar Pradesh cabinet under Mayawati, in the Kalyan Singh ministry earlier. On his birthday in April 2004, he was distributing free saris to poor women when a stampede broke out, killing 21 people, he was given a clean chit in this matter. In May 2009, he was elected to the 15th Lok Sabha from Lucknow by a margin over 40,000 votes over Rita Bahuguna Joshi of Indian National Congress.
The seat was earlier held by former BJP President Atal Bihari Vajpayee since 1991 for four consecutive terms. Despite an enormous electoral spending, Akhilesh Das of Bahujan Samaj Party polled third, trailing by 70 thousand votes; as a Governor of Bihar, Tandon was praised for streamlining academic activities of the state universities. On 20 July 2019, Tandon was appointed as the 22nd Governor of Madhya Pradesh, replacing Anandiben Patel. "Lalji Tandon". Lok Sabha
This is a list of alumni of Brooklyn College, a senior college of the City University of New York, located in Brooklyn, New York, United States. Walter Adams and President of Michigan State University Glenn Altschuler, Dean of the Cornell University School of Continuing Education and Summer Sessions, noted for his work on the history of American popular culture Samuel Baskin and educational reformer and first President of the Union Institute & University Barbara Aronstein Black, Columbia University School of Law Carmen Fariña, New York City Schools Chancellor Leon M. Goldstein, President of Kingsborough Community College, acting Chancellor of the City University of New York Alfred Gottschalk, President of Hebrew Union College and leader in the Reform Judaism movement Donald Kagan, historian. Kung San people of the Kalahari desert in south-western Africa Richard J. Smith, Ralph E. Morrow Distinguished Professor of Physical Anthropology at Washington University in St. Louis Paul Davidson, macroeconomist, one of the leading spokesmen of the American branch of the Post Keynesian school in economics Israel Kirzner, economist David Laibman, Professor Emeritus of Economics at Brooklyn College.