2-Chlorobutane structure

Practically everything we ve said in previous chapters has been stated without any proof. We said in Section 6.8, for instance, that Markovnikov s rule is followed in alkene electrophilic addition reactions and that treatment of 1-butene with HC1 yields 2-chJorobutane rather than 1-chlorobutane. Similarly, we said in Section 11.7 that Zaitsev s rule is followed in elimination reactions and that treatment of 2-chlorobutane with NaOH yields 2-butene rather than 1-butene. But how do we know that these statements are correct The answer to these and many thousands of similar questions is that the structures of the reaction products have been determined experimentally. 

Organic chemists have found a way to draw complex molecular structures in a very simple way, by not showing the C and H atoms explicitly. A line structure represents a chain of carbon atoms by a zigzag line, where each short line indicates a bond and the end of each line represents a carbon atom. Atoms other than C and H are shown by their symbols. Double bonds are represented by a double line and triple bonds by a triple line. Because carbon almost always forms four bonds in organic compounds, there is no need to show the C—FI bonds explicitly. We just fill in the correct number of hydrogen atoms mentally compare the line structure of 2-chlorobutane, QT3C1TC1CF12C]T3 (3a), with its structural form (3b). Line... 

Oxidative catalysis over metal oxides yields mainly HC1 and C02. Catalysts such as V203 and Cr203 have been used with some success.49 50 In recent years, nanoscale MgO and CaO prepared by a modified aerogel/hypercritical drying procedure (abbreviated as AP-CaO) and AP-MgO, were found to be superior to conventionally prepared (henceforth denoted as CP) CP-CaO, CP-MgO, and commercial CaO/MgO catalysts for the dehydrochlorination of several toxic chlorinated substances.51 52 The interaction of 1-chlorobutane with nanocrystalline MgO at 200 to 350°C results in both stoichiometric and catalytic dehydrochlorination of 1-chlorobutane to isomers of butene and simultaneous topochemical conversion of MgO to MgCl2.53-55 The crystallite sizes in these nanoscale materials are of the order of nanometers ( 4 nm). These oxides are efficient due to the presence of high concentration of low coordinated sites, structural defects on their surface, and high-specific-surface area. 

Condensation of salicylaldehydes with 2-chloro-3-formylbutene and analogs gave 2-methylenechromcnc derivatives.227 The direct reaction of salicylaldehyde with 2-methyl-2-chlorobutane or 2-methylbutene with catalysts to give 2,2,3-trimethylchromene is reported in a patent228 The structure of the products from salicylaldehyde and dipheny-lenes229,230 has been revised, (see Section V,B).231... 

Locant (Section 2.12) In IUPAC nomenclature, a prefix that designates the atom that is associated with a particular structural unit. The locant is most often a number, and the structural unit is usually an attached substituent as in 2-chlorobutane. 

Molecules such as 2-chlorobutane are termed chiral. Chiral molecules exist as either of two stereoisomeric structures. These stereoisomers, a pair of nonsuperimposable mirror images, are called enantiomers. 

The following reaction takes place under second-order conditions (strong nucleophile), yet the structure of the product shows rearrangement. Also, the rate of this reaction is several thousand times faster than the rate of substitution of hydroxide ion on 2-chlorobutane under similar conditions. Propose a mechanism to explain the enhanced rate and rearrangement observed in this unusual reaction. ( Et is the abbreviation for ethyl.)... 

EXAMPLE 7.3 The 13C spectrum of 2-chlorobutane (Figure 7.1) exhibits signals at 8 11.01, 24.85, 33.33, and 60.38. Assign each signal to a specific carbon in the structure by correlating the observed chemical shifts with the predicted values ... 

Suppose we did not know the structure of 2-chlorobutane, just its molecular formula (C4H9C1). Could we have deduced its structure from the HSC and COSY correlations in Figures 13.6 and 13.9 ... 

If one of the hydrogens of butane is replaced by another group, say a chlorine atom, how many different chlorobutanes can we get You should find, by drawing the structures or using a model kit, that there are only two possibilities (Figure 6.4.5). 

Deduce structures for the 1,3-azoles that are produced from the following reactant combinations (i) l-chlorobutan-2-one and thiourea (ii) thiobenzamide and chloroacetaldehyde (iii) thioformamide and ethyl bromoacetate. 

Indicate whether each of the following structures is (i )-2-chlorobutane or (5)-2-chlorobutane. (Use models, if necessary.)... 

Ans. 1-Chlorobutane and 2-chlorobutane have the same carbon structure but differ from each other in the placement of the chlorine atom. The same is true in comparing 2-chloro-2-methylpropane and... 

Arts, (a) There is only one 1,1-dichloroethane, not a pair of enantiomers, since there is no stereocenter. (b) 2-Chlorobutane exists as a pair of enantiomers since there is a stereocenter (noted by ). The stereocenter has four different substituents H, Cl, CH3, C2H5. The other enantiomer is drawn as the mirror image of the first structure. 

Problem 17.11 points out the visualization difficulties in discussing enantiomers. One must always understand that there is only one pair of enantiomers for a compound with one stereocenter. It is correct to use either the pair of drawings in Problem 17.9(h) or the pair in Problem 17.11 to represent the enantiomers of 2-chlorobutane. It is incorrect to draw all four structures to represent 2-chloro-butane. 

Gerdil, R., Allemand, J. TOT/(dl)-2-chlorobutane unpublished X-ray structure (final = 0.056 for 1429 independent reflections)... 

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