Organic Chemistry

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  • Created on: 17-12-15 10:57
Chapter 18 Introducing Organic Chemistry 18.1 Which one of the following molecules is butane? A CH3CH2CH3 B CH3CH2CH2CH3 C CH3CH2CH=CH2 D CH3CH2CH2CH2CH3
Answer: B Comment Butane is B. You can either get this right because you have learnt it, or you can work it out. ‘But-’ shows a chain of four carbons; ‘-ane’ shows that there are only carbon–carbon single bonds in the chain.
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18.2 Which one of the following molecules is propene? A CH3CH=CH2 B CH3CH2CH3 C CH3CH2CH=CH2 D CH3CH2CH2CH3
Answer: A Comment ‘Prop-’ shows a three carbon chain, and ‘-ene’ shows that it contains a carbon–carbon double bond. The answer is therefore A.
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18.3 What is the name of this hydrocarbon? A pentane B 2-methylpropane C 3-methylbutane D 2-methylbutane
Comment The longest chain you can find in this molecule is four carbon atoms long, and if you look at the number of things that each carbon is attached to, there isn’t any room for carbon–carbon double bonds. So the name is based on butane. There is
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18.4 What is the name of the molecule CH3CH2CH2OH ? A propane B ethanol C propan-1-ol D propan-2-ol
Answer: C Comment The molecule contains an -OH group and this is shown by the ending ‘-ol’. There are three carbon atoms in a chain with no double bonds, and so the name will be based on propane. Finally, the -OH group is on the number 1 carbon ato
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18.5 CH3  What is the name of the molecule CH3CHCHCH3 ?  CH3 A hexane B 2,3-dimethylpropane C 2,3-dimethylbutane D 2,3-dimethylpentane
Answer: C Comment The longest chain is four carbons, and there aren’t any carbon–carbon double bonds. That means that the name is based on butane. There are two methyl groups attached to the second and third carbon atoms in the chain. The name is 2,
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18.5* This question is about 2,2,3-trimethylpentan-3-ol. The name gives you several bits of information about the structure of the molecule. Which one of the following bits of information is wrong? A The longest chain of carbon atoms in the molecule
Answer: C Comment A is true. The name contains the code ‘-pent-’ which shows 5 carbon atoms in the longest chain. B is true. The ‘-ol’ ending shows an -OH group, and the ‘-3-ol’ shows that it is on the third carbon in the chain. C is wrong. If the c
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18.6 How many isomers are there for the molecular formula C4H10? A 1 B 2 C 3 D 4 Answer: B Comment
Answer: B Comment There are two isomers of C4H10. They are butane and 2-methylpropane. You will find structures of both of them in chapter 18 of the book, but it would be better if you could just work out what they were from the names. Don’t try to
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18.7 Structural isomers are molecules with the same molecular formula, but with different structural formulae. A student was asked to draw all the isomers for pentane, C5H12, and came up with the following four structures. (i) CH3  CH2  CH2  CH2
Answer: D Comment The best way of drawing the isomers for a structure is to make sure that you always draw the longest carbon chain horizontally. That way, you are less likely to draw duplicates. Look carefully at structure (iv). It is drawn as if
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18.7* Which one of the following is not an isomer of C3H8O ? A CH3  CH2  CH2  OH B CH3  CH2  O  CH3 C CH3  CH  CH3  OH D CH2  CH2   CH2  O
Answer: D Comment This is really just a matter of counting the atoms. Structure D has 3 carbons, 6 hydrogens and 1 oxygen. That’s not the same as the molecular formula you are given in the question, and so can’t be an isomer. Isomers always have th
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18.8 But-2-ene, CH3CH=CHCH3 , is one of the structural isomers of C4H8. How many other structural isomers of this are there (in addition to this one) which contain a C=C double bond? A 1 B 2 C 3 D 4
Answer: B Comment C4H8 has two other structural isomers also containing a C=C double bond. They are but-1-ene and 2-methylpropene. You should be able to work out what these look like from their names, but the structures of all these isomers are giv
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Card 2

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18.2 Which one of the following molecules is propene? A CH3CH=CH2 B CH3CH2CH3 C CH3CH2CH=CH2 D CH3CH2CH2CH3

Back

Answer: A Comment ‘Prop-’ shows a three carbon chain, and ‘-ene’ shows that it contains a carbon–carbon double bond. The answer is therefore A.

Card 3

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18.3 What is the name of this hydrocarbon? A pentane B 2-methylpropane C 3-methylbutane D 2-methylbutane

Back

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Card 4

Front

18.4 What is the name of the molecule CH3CH2CH2OH ? A propane B ethanol C propan-1-ol D propan-2-ol

Back

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Card 5

Front

18.5 CH3  What is the name of the molecule CH3CHCHCH3 ?  CH3 A hexane B 2,3-dimethylpropane C 2,3-dimethylbutane D 2,3-dimethylpentane

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