SPECTROSCOPY 327 13.20 (b) The index of hydrogen deficiency is given by the following formula Index of hydrogen deficiency ==(CH,n+2-CH) The compound given contains eight carbons(CRH&); therefore, Index of hydrogen deficiency =2(C&Hi8-C8Hg) The proDonds(or one triple bond). Since the index of hydrogen deficiency is equal to 5,there blem specifies that the compound consumes 2 mol of hydrogen, and so it contains two must be three rings. (c) Chlorine substituents are equivalent to hydrogens when calculating the index of hydrogen deficiency. Therefore, consider CRHaCl, as equivalent to CHio. Thus, the index of hydrogen deficiency of this compound is 4. Index of hydrogen deficiency ==(C&Hi& -,o) Since the compound consumes 2 mol of hydrogen on catalytic hydrogenation, it must there- fore contain two rings (d) Oxygen atoms are ignored when calculating the index of hydrogen deficiency. Thus, CHOis treated as if it were CrH& Index of hydrogen deficiency =C& -CsHa Since the problem specifies that 2 mol of hydrogen is consumed on catalytic hydrogenation, this compound contains three rings (e) Ignoring the oxygen atoms in CHoo we treat this compound as if it were CHio- Index of hydrogen deficiency =(C8HI8-CgHio Because 2 mol of hydrogen is consumed on catalytic hydrogenation, there must be two rings (f) Ignore the oxygen, and treat the chlorine as if it were hydrogen. Thus, CHO CIO is treated as if it were C&Hio. Its index of hydrogen deficiency is 4, and it contains two rings. 13.21 Since each compound exhibits only a single peak in its H NMR spectrum, all the hydrogens are equivalent in each one. Structures are assigned on the basis of their molecular formulas and chemi sh (a) This compound has the molecular formula C&His and so must be an alkane. The 18 hydrogens re contributed by six equivalent methyl groups (CH3)CC(CH3)3 .,3, 3-Tetramethylbutane (b) A hydrocarbon with the molecular formula Cshio has an index of hydrogen deficiency of 1 and so is either a cycloalkane or an alkene. Since all ten hydrogens are equivalent, this com- und must be cyclopentane (61.5ppm) Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website13.20 (b) The index of hydrogen deficiency is given by the following formula: Index of hydrogen deficiency 1 2 (CnH2n2  CnHx) The compound given contains eight carbons (C8H8); therefore, Index of hydrogen deficiency 1 2 (C8H18  C8H8) 5 The problem specifies that the compound consumes 2 mol of hydrogen, and so it contains two double bonds (or one triple bond). Since the index of hydrogen deficiency is equal to 5, there must be three rings. (c) Chlorine substituents are equivalent to hydrogens when calculating the index of hydrogen deficiency. Therefore, consider C8H8Cl2 as equivalent to C8H10. Thus, the index of hydrogen deficiency of this compound is 4. Index of hydrogen deficiency 1 2 (C8H18  C8H10) 4 Since the compound consumes 2 mol of hydrogen on catalytic hydrogenation, it must there￾fore contain two rings. (d) Oxygen atoms are ignored when calculating the index of hydrogen deficiency. Thus, C8H8O is treated as if it were C8H8. Index of hydrogen deficiency 1 2 (C8H18  C8H8) 5 Since the problem specifies that 2 mol of hydrogen is consumed on catalytic hydrogenation, this compound contains three rings. (e) Ignoring the oxygen atoms in C8H10O2, we treat this compound as if it were C8H10. Index of hydrogen deficiency 1 2 (C8H18  C8H10) 4 Because 2 mol of hydrogen is consumed on catalytic hydrogenation, there must be two rings. ( f ) Ignore the oxygen, and treat the chlorine as if it were hydrogen. Thus, C8H9ClO is treated as if it were C8H10. Its index of hydrogen deficiency is 4, and it contains two rings. 13.21 Since each compound exhibits only a single peak in its 1 H NMR spectrum, all the hydrogens are equivalent in each one. Structures are assigned on the basis of their molecular formulas and chemi￾cal shifts. (a) This compound has the molecular formula C8H18 and so must be an alkane. The 18 hydrogens are contributed by six equivalent methyl groups. (b) A hydrocarbon with the molecular formula C5H10 has an index of hydrogen deficiency of 1 and so is either a cycloalkane or an alkene. Since all ten hydrogens are equivalent, this com￾pound must be cyclopentane. Cyclopentane ( 1.5 ppm) (CH3)3CC(CH3)3 2,2,3,3-Tetramethylbutane ( 0.9 ppm) SPECTROSCOPY 327 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website