Carbon Lewis structure

Representing a two electron covalent bond by a dash (—) the Lewis structures for hydrogen fluoride fluorine methane and carbon tetrafluoride become... 

Lewis s concept of shared electron parr bonds allows for four electron double bonds and SIX electron triple bonds Carbon dioxide (CO2) has two carbon-oxygen double bonds and the octet rule is satisfied for both carbon and oxygen Similarly the most stable Lewis structure for hydrogen cyanide (HCN) has a carbon-nitrogen triple bond... 

Multiple bonds are very common m organic chemistry Ethylene (C2H4) contains a carbon-carbon double bond m its most stable Lewis structure and each carbon has a completed octet The most stable Lewis structure for acetylene (C2H2) contains a carbon-carbon triple bond Here again the octet rule is satisfied... 

Section 1 3 The most common kind of bonding involving carbon is covalent bond ing A covalent bond is the sharing of a pair of electrons between two atoms Lewis structures are written on the basis of the octet rule, which limits second row elements to no more than eight electrons m their valence shells In most of its compounds carbon has four bonds... 

Molecular models such as the one shown often do not explicitly show double and triple bonds Write a Lewis structure for this hydrocarbon showing the location of any multiple bonds Specify the hybndization state of each carbon (You can view this model in more detail on Learn mg By Modeling)... 

Draw Lewis structures for allyl cation. Where is the positive charge Examine atomic charges as well as the electrostatic potential map for localized and delocalized forms of allyl cation. Which carbon (s) carries the charge in each ... 

Compare atomic charges and electrostatic potential maps for imidazole NH protonated and imidazole Nprotonated. In which ion is the positive charge more delocalized Compare carbon-nitrogen bond distances in each ion to those in imidazole as a standard. Are these distances consistent with the bonding patterns shown above for each ion Draw whatever Lewis structures are needed to describe each ion s geometry and charge distribution. 

Examine the eleetrostatic potential map of eaeh nueleophile (enamine, silyl enol ether, lithium enolate and enol) with emphasis on the face of the nucleophilic alkene carbon. Rank the nucleophiles from most electron rich to least electron rich. What factors are responsible for this order (Hint For each molecule, consider an alternative Lewis structure to that given above that places a negative charge on the nucleophilic carbon.)... 

Examine the lowest-unoccupied molecular orbital (LUMO) in benzenium ion. On which carbon(s) is it most concentrated Draw a Lewis structure (or series of Lewis structures) for benzenium ion, and locate the positive charge. Is it located on the same carbons where the LUMO is concentrated Explain. 

Examine the geometry of methylbenzyne. Measure carbon-earbon distances. Which 7C bonds are deloealized and whieh are localized Is there really a triple bond (Compare bond distance to triple bond in hexa-l,5-dien-3-yne and to partial double bonds in benzene). Are you able to draw a single Lewis structure whieh adequately represents the geometry of the molecule ... 

Draw appropriate Lewis structures for pyrrole. How many K electrons does pyrrole have Is pyrrole aromatic Would you expect the three carbon-carbon bonds to be approximately the same length Explain. Examine the actual geometry of pyrrole. Are the bonds the same length ... 

Compare the geometry of maleic anhydride+propene, the ene transition state, to those of the reactants (maleic anhydride and propene). Is bond making and breaking occurring at once In particular, is the migrating hydrogen partially bonded to two carbons (rather than being fully bonded to one carbon ) Draw a Lewis structure to represent the transition state. Use dashed lines (.. and to represent partial bonds. 

There are several ways to choose the more plausible of two structures differing in their arrangement of atoms. As pointed out in Example 7.1, the fact that carbon almost always forms four bonds leads to the correct structure for ethane. Another approach involves a concept called formal charge, which can be applied to any atom within a Lewis structure. The formal charge is the difference between the number of valence electrons in the free atom and the number assigned to that atom in the Lewis structure. The assigned electrons include—... 

Oxalic acid, H2C204, is a poisonous compound found in rhubarb leaves. Draw the Lewis structure for oxalic acid. There is a single bond between the two carbon atoms, each hydrogen atom is bonded to an oxygen atom, and each carbon is bonded to two oxygen atoms. 

Two different molecules have the formula C2H2C12. Draw a Lewis structure for each molecule. (All the H and Cl atoms are bonded to carbon. The two carbon atoms are bonded to each other.)... 

Several compounds have the formula C3H60. Write Lewis structures for two of these compounds where the three carbon atoms are bonded to each other in a chain. The hydrogen and the oxygen atoms are bonded to the carbon atoms. 

Benzene, C6H(l, is another molecule best described as a resonance hybrid. It consists of a planar hexagonal ring of six carbon atoms, each one having a hydrogen atom attached to it. One Lewis structure that contributes to the resonance hybrid is shown in (11) it is called a Kekulc structure. The structure is normally written as a line structure (see Section C), a simple hexagon with alternating single and double lines (12). 

Now consider the alkynes, hydrocarbons with carbon-carbon triple bonds. The Lewis structure of the linear molecule ethyne (acetylene) is H—O C- H. To describe the bonding in a linear molecule, we need a hybridization scheme that produces two equivalent orbitals at 180° from each other this is sp hybridization. Each C atom has one electron in each of its two sp hybrid orbitals and one electron in each of its two perpendicular unhybridized 2p-orbitals (43). The electrons in the sp hybrid orbitals on the two carbon atoms pair and form a carbon—carbon tr-bond. The electrons in the remaining sp hybrid orbitals pair with hydrogen Ls-elec-trons to form two carbon—hydrogen o-bonds. The electrons in the two perpendicular sets of 2/z-orbitals pair with a side-by-side overlap, forming two ir-honds at 90° to each other. As in the N2 molecule, the electron density in the o-bonds forms a cylinder about the C—C bond axis. The resulting bonding pattern is shown in Fig. 3.23. 

Acrylonitrile, CH,CHCN, is used in the synthesis of acrylic fibers (polyacrylonitriles), such as Orion. Write the Lewis structure of acrylonitrile and describe the hybrid orbitals on each carbon atom. What are the approximate values of the bond angles ... 

Draw Lewis structures for each of the following species and predict the hybridization at each carbon atom ... 

The Lewis structure of caffeine, C8H 0N4O2, a common stimulant, is shown below, (a) Give the hybridization of each atom other than hydrogen and predict the bond angles about that atom, (b) On the basis of your answers in part (a), estimate the bond angles around each carbon and nitrogen atom. 

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