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IB DP Chemistry: SL复习笔记11.1.1 Index of Hydrogen Deficiency

Category: IB课程, 教材笔记, 福利干货 Date: 2022年8月4日 下午6:02

Index of Hydrogen Deficiency

 

  • The?degree of unsaturation?or?index of hydrogen deficiency?provides information about the number of double or triple bonds in a molecule
  • The?IHD?is the number of hydrogen molecules, H2, needed to convert the molecule to the corresponding saturated, non-cyclic molecule
  • There are two ways to solve?IHD?problems. One way is to draw the structure and identify rings and double and triple bonds, counting each one as an?IHD?value of 1.
  • The second way is to use a formula,
    • For a compound containing CxHy,?IHD= (2x+2-y)/2
    • This is a little complicated, since for the formula to work you need to:
      • ignore O and S
      • count halogens as hydrogen
      • add one C and one H for every nitrogen in the formula

       

     

 

 

11.1.1-Index-of-Hydrogen-Deficiency-Examples-111.1.1-Index-of-Hydrogen-Deficiency-Examples-2

 

Index of Hydrogen Deficiency Examples

 

 

Worked Example

Deduce the Index of Hydrogen Deficiency in ethyne, C2H2, methyl benzene, C6H5CH3, and propanone, CH3COCH3

 

Answer:

 

Answer 1:?Ethyne, C2H2?IHD= 2?

 

11.1.1-IHD-Worked-Example-Answer-1 

Answer 2:?Methylbenzene, C6H5CH3,?IHD= 4?

 

11.1.1-IHD-Worked-Example-Answer-2 

Answer 3:?Propanone,CH3COCH3??IHD = 1

 

11.1.1-IHD-Worked-Example-Answer-3

 

 

 

Exam Tip

Drawing out the structure is a much faster way to solve IHD problems, but using the formula is helpful when you are struggling to draw the structure

 

 

 

 

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