Unit 9. Organic compounds

Transcription

1 Unit 9. Organic compounds Index 1.- How to Name Organic Compounds Types of Compounds...3 Exercises...6 Practice exam...9 Page 1 of 11

2 The IUPAC Naming (nomenclature) System 1.- How to Name Organic Compounds The general approach is as follows: The name given to any compound containing a chain of carbon atoms consists of three parts: The root of the name which appears in the middle (this is further divided into the carbon chain designation and the infix), The prefix which appears at the start; and The suffix which appears at the end. 1.- The Root This is divided into two sections: the chain designation and the infix. The chain designation tells us the number of carbon atoms contained in the longest continuous carbon chain in the molecule. This is based upon the Table given below. Chain Designation The infix tells us the nature of the carbon bonds. No. of C Atoms meth- 1 eth- 2 prop- 3 but- 4 pent- 5 hex- 6 hept- 7 oct- 8 non- 9 dec- 10 Infix Nature of Carbon an en yn yl Carbon Bonds only single bonds one or more double bonds one or more triple bonds attached group (not part of main carbon chain) 2.- The Suffix This tells us the class of compound to which the substance belongs. It is derived from the most important functional group in the molecule. The suffixes listed in the table below are given in their order of importance, the most important at the top, the least at the bottom. If more than one functional group is in the molecule, it is assigned to that class which has the more Page 2 of 11

3 important functional group. Suffix Class of Compound Functional group -oic acid acid -COOH -oate ester -COOR -al alkanal -CHO -one alkanone -CO- -ol alkanol -OH -e -hydrocarbon -C-C-C 3.- The Prefix This tells us the other atoms and groups of atoms attached to the main carbon chain. It may be single species such as halogen atoms, carbon chains smaller than the maincarbon chain, or even rings of carbon atoms. In naming, dashes are used to separate numbers and letters; commas are only used to separate numbers from other numbers. Names are given in one piece; there are no gaps between the pieces except when specifically stated in the naming system. Rules: First count the longest continuous carbon chain Study the type of bond between carbons Next add the suffix. If the molecule is a hydrocarbon the suffix is just e. Finally we must list the attached groups as prefixes. 2.- Types of Compounds Types of compounds Example alkanes Hydrocarbons having no double or triple bond functional groups 1. Find and name the longest continuous carbon chain. 2. Identify and name groups attached to this chain. 3. Number the chain consecutively, starting at the end nearest a substituent group. Page 3 of 11

4 alkene Alkenes are hydrocarbons which have carbon-carbon double bond 1. The ene suffix (ending) indicates an alkene or cycloalkene. 2. The longest chain chosen for the root name must include both carbon atoms of the double bond. 3. The root chain must be numbered from the end nearest a double bond carbon atom. 4. The smaller of the two numbers designating the carbon atoms of the double bond is used as the double bond locator. If more than one double bond is present the compound is named as a diene, triene or equivalent prefix indicating the number of double bonds, and each double bond is assigned a locator number. alkynes alkynes are hydrocarbons which have carbon-carbon triple bond functional groups. The yne suffix (ending) indicates an alkyne or cycloalkyne. Same rules than alkenes Halocarbons alcohols ethers organic compounds containing one or more halogens An alcohol is a carbon chain with a hydroxide (OH - ) attached a carbon chain bonded to an oxygen that is bonded to another carbon chain Take the name of the element attached (chlorine) and replace the -ine with -o (chloro). Use the same group prefixes to describe the amount. Name the carbon chain, using the suffix -anol Place a number in front to indicate what carbon the hydroxide is attached to Name the carbon chains like attached groups. Alphabetize these and place them before the word "ether". CF 3 CHBrCl is named 2- bromo-2-chloro-1,1,1- trifluoroethane. -CH 2 -CH 2 OH is named 1-propanol. OCH 2 is named ethyl methyl ether Page 4 of 11

5 aldehydes ketones carboxylic acids esters amines An aldehyde is a carbon chain with an oxygen double bonded to the last/first carbon. A ketone is a carbon chain with an oxygen bonded to a middle carbon A carboxylic acid is a carbon chain with an oxygen double bonded and a hydroxide bonded to the last/first carbon An ester is a carbon chain with an oxygen both double and single bonded to one carbon An amine is a carbon chain with an NH 2 bonded to it Use the appropriate prefix for carbon chain and use the suffix -anal. No position number is required Use the suffix -anone and use position numbers past propanone Use the suffix -anoic acid. No position number is required Name the group without an oxygen (R') first. Then name the R-COO- part using the suffix -anoate. Use the suffix -amine and a position number if necessary. CHO is named ethanal -CH 2 -CH 2 -CO- is named 2-pentanone CH 2 COOH is named propanoic acid COOCH 2 CH 2 CH 2 C H 3 is named butyl etanoate. CHNH 2 is named 2-propanamine Page 5 of 11

6 Exercises 1. Formula of the following: 2-methylpentane Butane Propene 2,3-dimethylbutane 2,2-dimethylbutane. 3-ethyl-2-methylhexane. Propene. 1- butene 3-methylhex-2-ene 1,1,1-trichloroethane 2-bromo-2-methylpropane. Methanol 2-methylpropan-1-ol ethane-1,2-diol Propanal 2-methylpentanal. Propanone pentan-3-one Page 6 of 11

7 2. Name the following CO- Page 7 of 11

8 3.- Formula of the following 2-bromopentane butanoic acid ethyl methanoate 1-butanol Propanal 1,1 dichloro-2,2-difluoroethane Trimethylamine 2-methyl-2-propanol 2,4-dimethylpentane. 3-methyl-1-butanol 1-butene 2-butene 3-bromo-2-chloropentane 4. Name of the following CH3CH2CH=CH2 CH3CH2OH CH3-CHOH-CH2-CH2OH CH3CH2-COO-CH2CH3 CH3-CH2-CHO CH3CH2-O-CH2CH2CH2CH3 CH3CH2CH2CH2COCH2CH3 COOH-CH2-CH2-COOH HCOOH CH3-CHCl-CH2-CH3 Page 8 of 11

9 5.- Name the following compounds: Page 9 of 11

10 Practice exam CH 2 -CH 2 -CH 2 -CHCl-CH 2 Cl 13 -CHI-CHCl-CHBr-CH CH 2 -CH 2 -CH 2 -COOH 14 -CH 2 -CH 2 -CH 2 -COO- CH 2 -CH CHOH-CH 2 -CHOH-CHOH CH 2 -CO- CH 2 -CO COO- CH 2 -CH H-COOH 20. -CO-CO-CH methylpent-1-ene or 3-methyl-1-pentene 31. ethyne methylpentan-1-ol 32. 1,2,3-trifluoropropane 23. methanol 33. methanal 24.pentan-2-one methylhexanoic acid 25. propanal 35. propyl methanoate ethylhexanoic acid methylhexane 27.ethanedioic acid ethyl-2,5-dimethylhexane 28. propanoic acid 38. 4,4-dimethylpent-1-ene 29. methyl pentanoate 39. 4,4-dimethylpent-2-yne 30.1-chloro-2-methylpropane methylpentan-2-ol Page 10 of 11

11 Answers practice exam 2,2,4-trimethylpentane 3-methylpentane 3-ethylhexane 2-methylpent-2-ene; 2-methyl-2-pentene 1,2- dichlorohexane 4- bromo- 3-chloro- 2 iodo-hexane Pentanoic acid Propyl pentanoate 5-methylhex-2-ene; 5-methyl-2-hexene Butanal propan-1-ol 2,3,5- hexanetriol 3-methylbutan-1-ol Propapanedioic acid butanone 3- methyl butanal 2,4- hexanedione Propyl ethanoate Methanoic acid 2,3 pentanedione CH= CH CH 2 F-CHF -CH 2 F OH H-CHO -CH 2 - CH 2 - CH-( ) -CH 2 -COOH HCOO- CH 2 - CH 2 - -CH 2 - CH 2 - CH 2 -CH( ) - COOH-COOH -CH( )- CH 2 -CH(CH 2- )-CH( ) - -CH 2 - COOH - C( ) 2 - CH 2 -CH =CH 2 -CH 2 - CH 2 - CH 2 - COO- - C( ) 2 - CH = -C - CH 2 Cl- CH( )- - CH( )- CH 2 -CHOH - Page 11 of 11