In the previous list “n” stands for normal. In this case the bond is from the first carbon of the longest chain. Three other prefixes that occur commonly are: sec- short for secondary tert- short for tertiary iso (no hyphen is used) Examples: 2161 sec-butyl

In the previous list “n” stands for normal. In this case the bond is from the first carbon of the longest chain. Three other prefixes that occur commonly are: sec- short for secondary tert- short for tertiary iso (no hyphen is used) Examples: 2162 sec-butyltert-butyl

In the previous list “n” stands for normal. In this case the bond is from the first carbon of the longest chain. Three other prefixes that occur commonly are: sec- short for secondary tert- short for tertiary iso (no hyphen is used) Examples: 2163 sec-butyltert-butylisobutyl

The term isoalkane is used to denote a branched chain alkane with a methyl group attached to the penultimate carbon atom of the main chain. 2164

The term isoalkane is used to denote a branched chain alkane with a methyl group attached to the penultimate carbon atom of the main chain. As the number of carbon atoms increase, the prefixes become less useful, because an increasingly large number of prefixes would be needed. In this case, the standard numbering scheme (described about nine slides later) is used. 2165

Structures of some alkanes 2166

Structures of some alkanes 2167

Structures of some alkanes 2168

Structures of some alkanes 2169

Structures of some alkanes 2170

Structures of some alkanes These are straight chain examples. 2171

Structures of some alkanes These are straight chain examples. Note that the alkanes have only single bonds. 2172

Branched alkanes 2173

Branched alkanes 2174

Branched alkanes

Branched alkanes methylbutane (the 2 is a bit redundant) 2176

Branched alkanes methylbutane (the 2 is a bit redundant) Number the longest chain so as to give the lowest number to the substituent (in this case a methyl group) off the main chain. 2177

2178

,3-dimethylpentane 2180

,3-dimethylpentane There is more than one form of the preceding compound. We will discuss later how to name the different forms of this compound. 2181

2182

Note: there is a methyl and an ethyl group off the main chain. 2183

Note: there is a methyl and an ethyl group off the main chain. 2184

and 6 bigger than 3 and 4 – so this is wrong numbering Note: there is a methyl and an ethyl group off the main chain. 2185

Note: there is a methyl and an ethyl group off the main chain. 2186

3-methyl-4-ethyloctane (complexity order) Note: there is a methyl and an ethyl group off the main chain. 2187

3-methyl-4-ethyloctane (complexity order) 4-ethyl-3-methyloctane (alphabetical order) Note: there is a methyl and an ethyl group off the main chain. 2188

Summary of the simple rules to name an alkane. Summary of the simple rules to name an alkane. Prefix + root + suffix 2189

Ways of depicting an alkane 2190

The impact of free rotation about carbon – carbon single bonds. 2191

When assigning groups in alphabetical order, the prefixes are not considered. For example, for an alkane with an ethyl and two methyl groups as substituents, the ethyl substituent group is named first, followed by the dimethyl. E.g. 4-ethyl-2,2-dimethylnonane and not 2,2-dimethyl-4-ethylnonane 2192

When you have two (or more) alkyl substituents, number the longest chain in the direction that gives the smallest number to the first named substituent. E.g. 3-ethyl-5-methylheptane and not 3-methyl-5-ethylheptane (Draw out the structure) Where there are two or more longest chains of identical length, select the chain with the greater number of substituents. E.g. 3-ethyl-2-methylhexane and not 3-isopropylhexane (Draw out the structure) 2193

Exercises: Draw the structures of: (1) 2,2,3-trimethylbutane (2) 4-ethyl-2-methylnonane (3) 2,4-dimethyloctane 2194

Exercises: Draw the structures of: (1) 4-isopropyldecane (2) 2-methyl-4-(1-methylethyl)heptane (3) 4-isopropyl-2-methylheptane (4) 5-tert-butylnonane 2195

Physical properties of the alkanes The series of straight-chain alkanes shows a very smooth gradation of physical properties. As the series is ascended, each additional CH 2 group contributes a fairly constant increment to the boiling point and to the density – and to a lesser extent to the melting point. This makes it possible to estimate the properties of an unknown member of the series from those of its neighbors. 2196

Alkenes 2197

Alkenes These are hydrocarbons with at least one or more double bonds. 2198

Alkenes These are hydrocarbons with at least one or more double bonds. The parent alkanes are used to name the alkene family of compounds. 2199

Alkenes These are hydrocarbons with at least one or more double bonds. The parent alkanes are used to name the alkene family of compounds. The name ending change is: ane ene 2200

alkane alkene structure ethane ethene 2201

alkane alkene structure ethane ethene propane propene 2202

alkane alkene structure butane butene 2203

alkane alkene structure butane butene In this case there are three possible compounds. 2204

alkane alkene structure butane butene In this case there are three possible compounds. 1-butene 2205

alkane alkene structure butane butene In this case there are three possible compounds. 1-butene The number 1 indicates on which carbon the double bond starts. 2206

alkane alkene structure butane butene In this case there are three possible compounds. 1-butene The number 1 indicates on which carbon the double bond starts. 2- butene 2207

alkane alkene structure butane butene In this case there are three possible compounds. 1-butene The number 1 indicates on which carbon the double bond starts. 2- butene 2208

alkane alkene structure butane butene In this case there are three possible compounds. 1-butene The number 1 indicates on which carbon the double bond starts. 2- butene cis-2-butene trans-2-butene 2209

Z and E isomers Some cases arise in which it is very difficult to name a compound unambiguously, e.g. 2210

Z and E isomers Some cases arise in which it is very difficult to name a compound unambiguously, e.g. 2211

Z and E isomers Some cases arise in which it is very difficult to name a compound unambiguously, e.g. Is this a cis or trans compound? 2212

Z and E isomers Some cases arise in which it is very difficult to name a compound unambiguously, e.g. Is this a cis or trans compound? A way to sort out this problem is to use the symbols 2213

Z and E isomers Some cases arise in which it is very difficult to name a compound unambiguously, e.g. Is this a cis or trans compound? A way to sort out this problem is to use the symbols Z (zusammen = together) 2214

Z and E isomers Some cases arise in which it is very difficult to name a compound unambiguously, e.g. Is this a cis or trans compound? A way to sort out this problem is to use the symbols Z (zusammen = together) E(entgegen = opposite) 2215

Rules 1. Compare the two groups on one carbon atom of the carbon-carbon double bond. 2216

Rules 1. Compare the two groups on one carbon atom of the carbon-carbon double bond. 2. Assign the two groups priorities using the Cahn- Ingold-Prelog rules for R and S configurations. 2217

Rules 1. Compare the two groups on one carbon atom of the carbon-carbon double bond. 2. Assign the two groups priorities using the Cahn- Ingold-Prelog rules for R and S configurations. 3. Repeat steps 1 and 2 for the second carbon of the carbon-carbon double bond. 2218

Rules 1. Compare the two groups on one carbon atom of the carbon-carbon double bond. 2. Assign the two groups priorities using the Cahn- Ingold-Prelog rules for R and S configurations. 3. Repeat steps 1 and 2 for the second carbon of the carbon-carbon double bond. 4. If the two groups of highest priority are on the same side of the double bond, we have the Z isomer. If the two groups are on opposite sides we have the E isomer. 2219

Arrange the atoms in decreasing order of atomic number, e.g. I, Br, Cl, S, P, F, O, N, C, H 2220