Aldehydes and Ketones Klein, D. (2012). Aldehydes and Ketones. En Organic Chemistry (pp. 916-920). USA: Wiley. Espacio de Formación Multimodal 20.2 Nomenclature 917 916 CHAPTER 20 Aldehydes and Ketones 20.2 Nomenclature DO YOU REMEMBER? Before you go on, be sure you understand the following topics. If necessary, review the suggested sections Nomenclature of Aldehydes to prepare for this chapter: Recall that four discrete steps are required to name most classes of organic compounds (as we UÊ À}>À`ÊÀi>}iÌÃÊ­-iVÌʣΰȮÊÊ UÊ ,iÌÀÃÞÌ iÌVÊ>>ÞÃÃÊ­-iVÌÊ£Ó°x® saw with alkanes, alkenes, alkynes, and alcohols): UÊ "Ý`>ÌÊvÊ>V ÃÊ­-iVÌʣΰ£ä® 1. Identify and name the parent. 6ÃÌÊÜÜÜ°ÜiÞ«ÕðVÊÌÊV iVÊÞÕÀÊÕ`iÀÃÌ>`}Ê>`ÊvÀÊÛ>Õ>LiÊ«À>VÌVi° Ê 2. Identify and name the substituents. 3. Assign a locant to each substituent. 4. Assemble the substituents alphabetically. Aldehydes are also named using the same four-step procedure. When applying this procedure 20.1 Introduction to Aldehydes and Ketones for naming aldehydes, the following guidelines should be followed: When naming the parent, the suffix “-al” indicates the presence of an aldehyde group: Aldehydes (RCHO) and ketones (R2CO) are similar in structure in that both classes of com- pounds possess a CO bond, called a carbonyl group: O Carbonyl Group H Butane Butanal O O When choosing the parent of an aldehyde, identify the longest chain that includes the carbon RH RR atom of the aldehydic group: An aldehyde A ketone The parent The carbonyl group of an aldehyde is flanked by a hydrogen atom, while the carbonyl group of must include HO a ketone is flanked by two carbon atoms. this carbon atom Aldehydes and ketones are responsible for many flavors and odors that you will readily recognize: = = H CO O O Parent Octane Parent Hexanal 3 O O H H When numbering the parent chain of an aldehyde, the aldehydic carbon is assigned number 1, HO despite the presence of alkyl substituents, U bonds, or hydroxyl groups: H Correct Incorrect Vanillin Cinnamaldehyde (R)-Carvone Benzaldehyde (Vanilla flavor) (Cinnamon flavor) (Spearmint flavor) (Almond flavor) 24 6 64 2 H 135 7 H 753 1 Many important biological compounds also exhibit the carbonyl moiety, including progester- one and testosterone, the female and male sex hormones. O OH O OH It is not necessary to include the locant in the name, because it is understood that the aldehydic O OH carbon is the number 1 position. As with all compounds, when a chirality center is present, the configuration is indicated at H H the beginning of the name; for example: H H H H O O O H Progesterone Testosterone Cl Simple aldehydes and ketones are industrially important; for example: O O (R)-2-chloro-3-phenylpropanal A cyclic compound containing an aldehyde group immediately adjacent to the ring is named as HH H3C CH3 a carbaldehyde: Formaldehyde Acetone O Acetone is used as a solvent and is commonly found in nail polish remover, while formaldehyde is used as a preservative in some vaccine formulations. Aldehydes and ketones are also used as build- H ing blocks in the syntheses of commercially important compounds, including pharmaceuticals and polymers. Compounds containing a carbonyl group react with a large variety of nucleophiles, affording a wide range of possible products. Due to the versatile reactivity of the carbonyl group, Cyclohexanecarbaldehyde aldehydes and ketones occupy a central role in organic chemistry. klein_c20_915-969hr2.indd 917 11/17/10 1:17 PM klein_c20_915-969hr2.indd 916 11/17/10 1:17 PM 20.2 Nomenclature 917 916 CHAPTER 20 Aldehydes and Ketones 918 CHAPTER 20 Aldehydes and Ketones 20.2 Nomenclature DO YOU REMEMBER? The International Union of Pure and Applied Chemistry (IUPAC) nomenclature also recognizes the common names of many simple aldehydes, including the three examples shown below: Before you go on, be sure you understand the following topics. If necessary, review the suggested sections Nomenclature of Aldehydes to prepare for this chapter: Recall that four discrete steps are required to name most classes of organic compounds (as we O O O UÊ À}>À`ÊÀi>}iÌÃÊ­-iVÌʣΰȮÊÊ UÊ ,iÌÀÃÞÌ iÌVÊ>>ÞÃÃÊ­-iVÌÊ£Ó°x® saw with alkanes, alkenes, alkynes, and alcohols): HH H C H H UÊ "Ý`>ÌÊvÊ>V ÃÊ­-iVÌʣΰ£ä® 1. Identify and name the parent. 3 6ÃÌÊÜÜÜ°ÜiÞ«ÕðVÊÌÊV iVÊÞÕÀÊÕ`iÀÃÌ>`}Ê>`ÊvÀÊÛ>Õ>LiÊ«À>VÌVi° Formaldehyde Acetaldehyde Benzaldehyde Ê 2. Identify and name the substituents. 3. Assign a locant to each substituent. Nomenclature of Ketones 4. Assemble the substituents alphabetically. Ketones, like aldehydes, are named using the same four-step procedure. When naming the par- Aldehydes are also named using the same four-step procedure. When applying this procedure ent, the suffix “-one” indicates the presence of a ketone group: 20.1 Introduction to Aldehydes and Ketones for naming aldehydes, the following guidelines should be followed: O When naming the parent, the suffix “-al” indicates the presence of an aldehyde group: Aldehydes (RCHO) and ketones (R2CO) are similar in structure in that both classes of com- pounds possess a CO bond, called a carbonyl group: O Butane Butanone The position of the ketone group is indicated using a locant. The IUPAC rules published in Carbonyl Group H 1979 dictate that this locant be placed immediately before the parent, while the IUPAC recom- Butane Butanal O O mendations released in 1993 and 2004 allow for the locant to be placed immediately before the When choosing the parent of an aldehyde, identify the longest chain that includes the carbon suffix “-one”: RH RR atom of the aldehydic group: O 3-heptanone An aldehyde A ketone or The parent 1357heptan-3-one The carbonyl group of an aldehyde is flanked by a hydrogen atom, while the carbonyl group of must include 642 a ketone is flanked by two carbon atoms. HO this carbon atom Both names above are acceptable IUPAC names. IUPAC nomenclature recognizes the common Aldehydes and ketones are responsible for many flavors and odors that you will readily names of many simple ketones, including the three examples shown below: recognize: O O = = H CO O O Parent Octane Parent Hexanal 3 O O O CH3 H H When numbering the parent chain of an aldehyde, the aldehydic carbon is assigned number 1, HO despite the presence of alkyl substituents, U bonds, or hydroxyl groups: H3C CH3 H Correct Incorrect Acetone Acetophenone Benzophenone Vanillin Cinnamaldehyde (R)-Carvone Benzaldehyde (Vanilla flavor) (Cinnamon flavor) (Spearmint flavor) (Almond flavor) 24 6 64 2 Although rarely used, IUPAC rules also allow simple ketones to be named as alkyl alkyl ketones. H 135 7 H 753 1 For example, 3-hexanone can also be called ethyl propyl ketone: Many important biological compounds also exhibit the carbonyl moiety, including progester- O one and testosterone, the female and male sex hormones. O OH O OH C It is not necessary to include the locant in the name, because it is understood that the aldehydic O OH carbon is the number 1 position. Ethyl propyl ketone As with all compounds, when a chirality center is present, the configuration is indicated at H H the beginning of the name; for example: H H H H O SKILLBUILDER O O 20.1 NAMING ALDEHYDES AND KETONES H Progesterone Testosterone Cl Simple aldehydes and ketones are industrially important; for example: LEARN the skill *ÀÛ`iÊ>ÊÃÞÃÌi>ÌVÊ­1* ®Ê>iÊvÀÊÌ iÊvÜ}ÊV«Õ`\ O O (R)-2-chloro-3-phenylpropanal A cyclic compound containing an aldehyde group immediately adjacent to the ring is named as HH H3C CH3 a carbaldehyde: O Formaldehyde Acetone O SOLUTION 8 Acetone is used as a solvent and is commonly found in nail polish remover, while formaldehyde is / iÊwÀÃÌÊÃÌi«ÊÃÊÌÊ`iÌvÞÊ>`Ê>iÊÌ iÊ«>ÀiÌ°Ê ÃiÊÌ iÊ- 79 used as a preservative in some vaccine formulations. Aldehydes and ketones are also used as build- STEP 1 H }iÃÌÊV >ÊÌ >ÌÊVÕ`iÃÊÌ iÊV>ÀLÞÊ}ÀÕ«]Ê>`ÊÌ iÊÕLiÀÊÌ iÊ 2 46 ing blocks in the syntheses of commercially important compounds, including pharmaceuticals `iÌvÞÊ>`Ê>iÊÌ iÊ 1 «>ÀiÌ° V >ÊÌÊ}ÛiÊÌ iÊV>ÀLÞÊ}ÀÕ«ÊÌ iÊÜiÃÌÊÕLiÀÊ«ÃÃLi\ and polymers. Compounds containing a carbonyl group react with a large variety of nucleophiles, 3 5 O affording a wide range of possible products. Due to the versatile reactivity of the carbonyl group, Cyclohexanecarbaldehyde aldehydes and ketones occupy a central role in organic chemistry. 3-nonanone klein_c20_915-969hr2.indd 917 11/17/10 1:17 PM klein_c20_915-969hr2.indd 916 11/17/10 1:17 PM klein_c20_915-969hr2.indd 918 11/17/10 1:17 PM 20.2 Nomenclature 917 918 CHAPTER 20 Aldehydes and Ketones 20.2 Nomenclature 919 20.2 Nomenclature The International Union of Pure and Applied Chemistry (IUPAC) nomenclature also recognizes iÝÌ]Ê`iÌvÞÊÌ iÊÃÕLÃÌÌÕiÌÃÊ>`Ê>ÃÃ}ÊV>ÌÃ\ the common names of many simple aldehydes, including the three examples shown below: STEP 2 Nomenclature of Aldehydes `iÌvÞÊ>`Ê>iÊÌ iÊ 4,4-dimethyl 8 Recall that four discrete steps are required to name most classes of organic compounds (as we O O O ÃÕLÃÌÌÕiÌð 79 saw with alkanes, alkenes, alkynes, and alcohols): STEP 3 2 46 ÃÃ}Ê>ÊV>ÌÊÌÊi>V Ê 1 HH H3C H H 3 5 1. Identify and name the parent. ÃÕLÃÌÌÕiÌ° 6-ethyl O 2. Identify and name the substituents. Formaldehyde Acetaldehyde Benzaldehyde >Þ]Ê>ÃÃiLiÊÌ iÊÃÕLÃÌÌÕiÌÃÊ>« >LiÌV>Þ\ÊÈiÌ Þ{]{`iÌ ÞÎ>i°Ê ivÀiÊ 3. Assign a locant to each substituent. Nomenclature of Ketones VVÕ`}]ÊÜiÊÕÃÌÊ>Ü>ÞÃÊV iVÊÌÊÃiiÊvÊÌ iÀiÊ>ÀiÊ>ÞÊV À>ÌÞÊViÌiÀðÊ/ ÃÊV«Õ`Ê 4.