Section B-Alkanes and cycloalkanes CH2CHg Fig.5.5-Ethyl-2,2-dimethyldecane CH CH Fig.6.5-Ethyl-2,2,6-trimethyldecane. The prefixes di-,tri-,tetra-etc.are used for identical substituents,but the order in which they are written is still dependent on the alphabetical order of the substituents themselves (i.e.ignore the di-,tri-,tetra-,et cetera).For example,the structure in Fig.5 is called 5-ethyl-2,2-dimethyldecane and not 2,2-dimethyl-5-ethyldecane. Identical substituents can be in different positions on the chain,but the same rules apply.For example,the structure in Fig.6 is called 5-ethyl-2,2,6-trimethyldecane. In some structures,it is difficult to decide which end of the chain to number from.For example,two different substituents might be placed at equal distances from either end of the chain.If that is the case,the group with alphabetical prior- ity should be given the lowest numbering.For example,the structure in Fig.7a is 3-ethyl-5-methylheptane and not 5-ethyl-3-methylheptane. However,there is another rule which might take precedence over the above rule.The structure (Fig.7c)has ethyl and methyl groups equally placed from each end of the chain,but there are two methyl groups to one ethyl group.Num- bering should be chosen such that the smallest total is obtained.In this example the structure is called 5-ethyl-3,3-dimethylheptane(Fig.7c)rather than 3-ethyl- 5,5-dimethylheptane (Fig.7b)since 5+3+3=11 is less than 3+5+5=13. Cycloalkanes Cycloalkanes are simply named by identifying the number of carbons in the ring and prefixing the alkane name with cyclo (Fig.8). 7入5入3入1 7入5入3入1g1入3入5入7 CH. Methyl Ethy Methyl Fig.7.(a)3-Ethyl-5-methyheptane;(b)incorrect numbering:(c)5-ethyl-3,3-dimethylheptane. 0>口9○ Fig.B.(a)Cyclopropane:(b)cyclobutane:(c)cyclopentane:(d)cyclohexane
The prefixes di-, tri-, tetra- etc. are used for identical substituents, but the order in which they are written is still dependent on the alphabetical order of the substituents themselves (i.e. ignore the di-, tri-, tetra-, et cetera). For example, the structure in Fig. 5 is called 5-ethyl-2,2-dimethyldecane and not 2,2-dimethyl-5-ethyldecane. Identical substituents can be in different positions on the chain, but the same rules apply. For example, the structure in Fig. 6 is called 5-ethyl-2,2,6-trimethyldecane. In some structures, it is difficult to decide which end of the chain to number from. For example, two different substituents might be placed at equal distances from either end of the chain. If that is the case, the group with alphabetical priority should be given the lowest numbering. For example, the structure in Fig. 7a is 3-ethyl-5-methylheptane and not 5-ethyl-3-methylheptane. However, there is another rule which might take precedence over the above rule. The structure (Fig. 7c) has ethyl and methyl groups equally placed from each end of the chain, but there are two methyl groups to one ethyl group. Numbering should be chosen such that the smallest total is obtained. In this example, the structure is called 5-ethyl-3,3-dimethylheptane (Fig. 7c) rather than 3-ethyl- 5,5-dimethylheptane (Fig. 7b) since 533 = 11 is less than 355 = 13. Cycloalkanes Cycloalkanes are simply named by identifying the number of carbons in the ring and prefixing the alkane name with cyclo (Fig. 8). 24 Section B – Alkanes and cycloalkanes H3C CH3 CH2CH3 H3C CH3 CH2CH3 5 10 1 2 Fig. 5. 5-Ethyl-2,2-dimethyldecane. H3C CH3 CH2CH3 H3C CH3 CH2CH3 CH3 CH3 1 2 5 10 Fig. 6. 5-Ethyl-2,2,6-trimethyldecane. CH3 CH2CH3 Methyl Ethyl 5 3 1 CH3 CH2CH3 CH3 CH2CH3 H3C H3C Ethyl b) Methyl 7 5 3 1 1 3 5 7 Methyl 7 Ethyl c) Fig. 7. (a) 3-Ethyl-5-methylheptane; (b) incorrect numbering; (c) 5-ethyl-3,3-dimethylheptane. a) b) c) d) Fig. 8. (a) Cyclopropane; (b) cyclobutane; (c) cyclopentane; (d) cyclohexane
B3-Nomenclature Fig.9.(a)Methylcyclohexane:(b)1-cyclohexyloctane;(c)1-ethyl-3-methylcyclohexane Branched Cycloalkanes consisting of a cycloalkane moiety linked to an alkane moiety are cyclohexanes usually named such that the cycloalkane is the parent system and the alkane moiety is considered to be an alkyl substituent.Therefore,the structure in Fig.9a is methylcyclohexane and not cyclohexylmethane.Note that there is no need to number the cycloalkane ring when only one substituent is present. If the alkane moiety contains more carbon atoms than the ring,the alkane moiety becomes the parent system and the cycloalkane group becomes the substituent.For example,the structure in Fig.9b is called 1-cyclohexyloctane and not octylcyclohexane.In this case,numbering is necessary to identify the position of the cycloalkane on the alkane chain. Multi-branched Branched cycloalkanes having different substituents are numbered such that the cycloalkanes alkyl substi the rest of the ring is the eth以3 cture in Fig. 9c is called 1 ethyl-3-m hexane.The last name total addin the 6which is higher than the total obtaine
B3 – Nomenclature 25 Branched Cycloalkanes consisting of a cycloalkane moiety linked to an alkane moiety are cyclohexanes usually named such that the cycloalkane is the parent system and the alkane moiety is considered to be an alkyl substituent. Therefore, the structure in Fig. 9a is methylcyclohexane and not cyclohexylmethane. Note that there is no need to number the cycloalkane ring when only one substituent is present. If the alkane moiety contains more carbon atoms than the ring, the alkane moiety becomes the parent system and the cycloalkane group becomes the substituent. For example, the structure in Fig. 9b is called 1-cyclohexyloctane and not octylcyclohexane. In this case, numbering is necessary to identify the position of the cycloalkane on the alkane chain. Multi-branched Branched cycloalkanes having different substituents are numbered such that the cycloalkanes alkyl substituent having alphabetical priority is at position 1. The numbering of the rest of the ring is then carried out such that the substituent positions add up to a minimum. For example, the structure in Fig. 9c is called 1-ethyl-3-methylcyclohexane rather than 1-methyl-3-ethylcyclohexane or 1-ethyl-5-methylcyclohexane. The last name is incorrect since the total obtained by adding the substituent positions together is 51 6 which is higher than the total obtained from the correct name (i.e. 134). 8 a) CH3 b) c) 1 1 3 5 Fig. 9. (a) Methylcyclohexane; (b) 1-cyclohexyloctane; (c) 1-ethyl-3-methylcyclohexane.
Section C-Functional groups C1 RECOGNITION OF FUNCTIONAL GROUPS Key Notes Definition carbon anc contain bonds other C-H. Some of the most common functional groups in organic chemistry hols,phen Related topics Definition(B1) Aliphatic and aromatic Drawing structures(B2) functional groups (C2) Definition A functional group is a portion of an organic molecule which consists of atoms other than carbon and hydrogen,or which contains bonds other than C-C and C-H bonds.For example,ethane (Fig.1a)is an alkane and has no functional group.All the atoms are carbon and hydrogen and all the bonds are C-C and C-H. Ethanoic acid on the other hand (Fig.1b),has a portion of the molecule (boxed portion)which contains atoms other than carbon and hydrogen,and bonds other than C-H and C-C.This portion of the molecule is called a functional group- in this case a carboxylic acid. Carboxylic acid a unctional group H3C一CH3 OH Fig.1.(a)Ethane;(b)ethanoic acid Common The following are some of the more common functional groups in organic functional groups chemistry. .functional groups which contain carbon and hydrogen only (Fig.2); b) c R一C三C一R Fig.2.(a)Alkene;(b)alkyne:(c)aromatic
Section C – Functional groups C1 RECOGNITION OF FUNCTIONAL GROUPS Definition A functional group is a portion of an organic molecule which consists of atoms other than carbon and hydrogen, or which contains bonds other than C–C and C–H bonds. For example, ethane (Fig. 1a) is an alkane and has no functional group. All the atoms are carbon and hydrogen and all the bonds are C–C and C–H. Ethanoic acid on the other hand (Fig. 1b), has a portion of the molecule (boxed portion) which contains atoms other than carbon and hydrogen, and bonds other than C—H and C—C. This portion of the molecule is called a functional group – in this case a carboxylic acid. Common The following are some of the more common functional groups in organic functional groups chemistry. ● functional groups which contain carbon and hydrogen only (Fig. 2); Key Notes Functional groups are portions of a molecule which contain atoms other than carbon and hydrogen, or which contain bonds other than C–C and C–H. Some of the most common functional groups in organic chemistry are alkenes, alkynes, aromatics, nitriles, amines, amides, nitro compounds, alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, acid chlorides, acid anhydrides, esters, alkyl halides, thiols, and thioethers. Related topics Definition (B1) Drawing structures (B2) Aliphatic and aromatic functional groups (C2) Common functional groups Definition H3C CH3 H3C C OH O Carboxylic acid a) b) functional group Fig. 1. (a) Ethane; (b) ethanoic acid. R C C R R R RCCR a) b) c) Fig. 2. (a) Alkene; (b) alkyne; (c) aromatic
28 Section C-Functional groups functional groups which contain nitrogen(Fig.3): a) c) R一C三N R-N-R R—NO2 Fig.3.(a)Nitrile:(b)amine:(c)amide:(d)nitro. functional groups involving single bonds and which contain oxygen (Fig.4); b) R OR Fig.4.(Alcohol or alkanol:(b)ether. functional groups involving double bonds and which contain oxygen(Fig.5); functional groups which contain a halogen atom (Fig.6) ②.toee,e5aBskaMhaeorhag8nakaneX=caBc functional groups which contain sulfur(Fig.7). a)R-SHb)R-S一R Fig.7.(a)Thiol:(b)thioethe
28 Section C – Functional groups ● functional groups which contain nitrogen (Fig. 3); ● functional groups involving single bonds and which contain oxygen (Fig. 4); ● functional groups involving double bonds and which contain oxygen (Fig. 5); ● functional groups which contain a halogen atom (Fig. 6); ● functional groups which contain sulfur (Fig. 7). RCN R C O R N NR2 R R R NO2 a) b) c) d) Fig. 3. (a) Nitrile; (b) amine; (c) amide; (d) nitro. R OH R O R a) b) Fig. 4. (a) Alcohol or alkanol; (b) ether. R H C O R R C O R OH C O R Cl C O R O C O R C O O H R OR C O R NR2 C O e) f) g) h) a) d) b) c) Fig. 5. (a) Aldehyde or alkanal; (b) ketone or alkanone; (c) carboxylic acid; (d) carboxylic acid chloride; (e) carboxylic acid anhydride; (f) ester; (g) amide; (h) phenol. R X R Cl C X O a) b) c) Fig. 6. (a) Aryl halide (X F, Cl, Br, I); (b) alkyl halide or halogenoalkane (X = F, Cl, Br, I); (c) carboxylic acid chloride. a) b) R SH R S R Fig. 7. (a) Thiol; (b) thioether.
Section C-Functional groups C2 ALIPHATIC AND AROMATIC FUNCTIONAL GROUPS Key Notes Aliphatic functional Functional groups are defined as aliphatic if there is no aromatic ring groups directly attached to them.It is possible to have an aromatic molecule con- taining an aliphatic functional group if the aromatic ring is not directly attached to the functional group. Aromatic functional Functional groups are defined as aromatic if they have an aromatic ring groups directly attached to them.In the case of esters and amides,the aromatic ring must be attached to the carbonyl side of the functional group.If the aromatic ring is attached to the heteroatom,the functional groups are defined as aliphatic. Related topic Recognition of functional groups(C1) Functional groups ca be cassed asa c or atic. An alip group i e w ring directly attached group(Fig.1a and b) Fig.1.(a)Aliphatic ketone:(b)aliphatic ester;(c)aromatic carboxylic acid:(d)aromatic ketone. netionaroup品sgp家ad】 An aromatic functional group is one where an aromatic ring is directly attached to There is one complication involving esters and amides.These functional groups are defined as aromatic or aliphatic depending on whether the aryl group is directly attached to the carbonyl end of the functional group,that is,Ar-CO-X.If the aromatic ring is attached to the heteroatom instead,then the ester or amide is classed as an aliphatic amide(Fig.2). Fig.2.(a)Aromatic ester;(b)aliphatic ester;(c)aromatic amide:(d)aliphatic amide
Section C – Functional groups C2 ALIPHATIC AND AROMATIC FUNCTIONAL GROUPS Aliphatic Functional groups can be classed as aliphatic or aromatic. An aliphatic functional functional groups group is one where there is no aromatic ring directly attached to the functional group (Fig. 1a and b). Aromatic An aromatic functional group is one where an aromatic ring is directly attached to functional groups the functional group (Fig. 1c and d). There is one complication involving esters and amides. These functional groups are defined as aromatic or aliphatic depending on whether the aryl group is directly attached to the carbonyl end of the functional group, that is, Ar–CO–X. If the aromatic ring is attached to the heteroatom instead, then the ester or amide is classed as an aliphatic amide (Fig. 2). Key Notes Functional groups are defined as aliphatic if there is no aromatic ring directly attached to them. It is possible to have an aromatic molecule containing an aliphatic functional group if the aromatic ring is not directly attached to the functional group. Functional groups are defined as aromatic if they have an aromatic ring directly attached to them. In the case of esters and amides, the aromatic ring must be attached to the carbonyl side of the functional group. If the aromatic ring is attached to the heteroatom, the functional groups are defined as aliphatic. Related topic Recognition of functional groups (C1) Aromatic functional groups Aliphatic functional groups CH CH3 C O CH3 H3C CO2CH2CH3 C O CH3 CO2H a) b) c) d) Fig. 1. (a) Aliphatic ketone; (b) aliphatic ester; (c) aromatic carboxylic acid; (d) aromatic ketone. C O O H3C C O O CH3 NH C O H3C C N O CH3 CH3 a) b) c) d) Fig. 2. (a) Aromatic ester; (b) aliphatic ester; (c) aromatic amide; (d) aliphatic amide