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Unformatted text preview: 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry Boundless Chemistry Organic Chemistry Functional Group Names, Properties, and Reactions … 1/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry Functional Groups Functional groups refer to speci c atoms bonded in a certain arrangement that give a compound certain physical and chemical properties. LEARNING OBJECTIVES De ne the term “functional group” as it applies to organic molecules KEY TAKEAWAYS Key Points Functional groups are often used to “functionalize” a compound, a ording it di erent physical and chemical properties than it would have in its original form. Functional groups will undergo the same type of reactions regardless of the compound of which they are a part; however, the presence of certain functional groups within close proximity can limit reactivity. Functional groups can be used to distinguish similar compounds from each other. Key Terms functional group: A speci c grouping of elements that is characteristic of a class of compounds, and determines some properties and reactions of that class. functionalization: Addition of speci c functional groups to a ord the compound new, desirable properties. … 2/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry The Role of Functional Groups In organic chemistry, a functional group is a speci c group of atoms or bonds within a compound that is responsible for the characteristic chemical reactions of that compound. The same functional group will behave in a similar fashion, by undergoing similar reactions, regardless of the compound of which it is a part. Functional groups also play an important part in organic compound nomenclature; combining the names of the functional groups with the names of the parent alkanes provides a way to distinguish compounds. The atoms of a functional group are linked together and to the rest of the compound by covalent bonds. The rst carbon atom that attaches to the functional group is referred to as the alpha carbon; the second, the beta carbon; the third, the gamma carbon, etc. Similarly, a functional group can be referred to as primary, secondary, or tertiary, depending on if it is attached to one, two, or three carbon atoms. Classi cation of alcohols: Alcohols are a common functional group (-OH). They can be classi ed as primary, secondary, or tertiary, depending on how many carbon atoms the central carbon is attached to. Functional Groups and Reactivity Functional groups play a signi cant role in directing and controlling organic reactions. Alkyl chains are often nonreactive, and the direction of site-speci c reactions is di cult; unsaturated alkyl chains with the presence of functional groups allow for higher reactivity and speci city. Often, compounds are functionalized with speci c groups for a speci c chemical reaction. Functionalization refers to the addition of functional … 3/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry groups to a compound by chemical synthesis. Through routine synthesis methods, any kind of organic compound can be attached to the surface. In materials science, functionalization is employed to achieve desired surface properties; functional groups can also be used to covalently link functional molecules to the surfaces of chemical devices. In organic chemistry, the most common functional groups are carbonyls (C=O), alcohols (-OH), carboxylic acids (CO2H), esters (CO2R), and amines (NH2). It is important to be able to recognize the functional groups and the physical and chemical properties that they a ord compounds. Organic C… C… Organic chemistry functional groups lesson: This video provides a great overview of the various functional groups in organic chemistry. Alcohols Alcohols are functional groups characterized by the presence of an -OH group. LEARNING OBJECTIVES Identify the general properties of the alcohol functional group … 4/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry KEY TAKEAWAYS Key Points Due to the presence of an -OH group, alcohols can hydrogen bond. This leads to higher boiling points compared to their parent alkanes. Alcohols are polar in nature. This is attributed to the di erence in electronegativity between the carbon and the oxygen atoms. In chemical reactions, alcohols often cannot leave the molecule on their own; to leave, they often become protonated to water, which is a better leaving group. Alcohols also can become deprotonated in the presence of a strong base. Key Terms alkane: Any of the saturated hydrocarbons—including methane, ethane, and compounds with long carbon chain known as para ns, etc.— that have a chemical formula of the form CnH2n+2. aldehyde: Any of a large class of reactive organic compounds (R·CHO) having a carbonyl functional group attached to one hydrocarbon radical and a hydrogen atom. carboxylic acid: Any of a class of organic compounds containing a carboxyl functional group—a carbon with a double bond to an oxygen and a single bond to another oxygen, which is in turn bonded to a hydrogen. leaving group: In organic chemistry, the species that leaves the parent molecule following a substitution reaction. … 5/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry Alcohols are organic compounds in which the hydroxyl functional group (-OH) is bound to a carbon atom. Alcohols are an important class of molecules with many scienti c, medical, and industrial uses. Nomenclature of Alcohols According to the IUPAC nomenclature system, an alcohol is named by dropping the terminal “-e” of the parent carbon chain (alkane, alkene, or alkyne in most cases) and the addition of “-ol” as the ending. If the location of the hydroxyl group must be speci ed, a number is inserted between the parent alkane name and the “-ol” (propan-1-ol) or before the IUPAC name (1-propanol). If a higher priority group is present, such as an aldehyde, ketone or carboxylic acid, then it is necessary to use the pre x “hydroxy-” instead of the ending “-ol.” Alcohols are classi ed as primary, secondary, or tertiary, based upon the number of carbon atoms connected to the carbon atom that bears the hydroxyl group. Structure and Physical Properties of Alcohols The structure of an alcohol is similar to that of water, as it has a bent shape. This geometrical arrangement re ects the e ect of electron repulsion and the increasing steric bulk of the substituents on the central oxygen atom. Like water, alcohols are polar, The alcohol functional group: Alcohols are characterized by the presence of an -OH group, which is generally in a bent shape, like that of water. containing an unsymmetrical distribution of charge between the oxygen and hydrogen atoms. The high electronegativity of the oxygen compared to carbon leads to the shortening and strengthening of the OH bond. The presence of the -OH groups allows for hydrogen bonding with other -OH groups, hydrogen atoms, and other molecules. Since alcohols are able to hydrogen bond, their boiling points are higher than those of their parent molecules. … 6/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry Alcohols are able to participate in many chemical reactions. They often undergo deprotonation in the presence of a strong base. This weak acid behavior results in the formation in an alkoxide salt and a water molecule. Hydroxyl groups alone are not considered good leaving groups. Often, their participation in nucleophilic substitution reactions is instigated by the protonation of the oxygen atom, leading to the formation a water moiety—a better leaving group. Alcohols can react with carboxylic acids to form an ester, and they can be oxidized to aldehydes or carboxylic acids. Alcohols have many uses in our everyday world. They are found in beverages, antifreeze, antiseptics, and fuels. They can be used as preservatives for specimens in science, and they can be used in industry as reagents and solvents because they display an ability to dissolve both polar and non-polar substances. Ethers Ethers are a class of organic compounds characterized by an oxygen atom connected to two alkyl or aryl groups. LEARNING OBJECTIVES De ne the term “ether” as it relates to organic compounds KEY TAKEAWAYS Key Points Ethers have relatively low boiling points due to their inability to form hydrogen bonds with each other. Due to the electronegativity di erence between the oxygen and carbon atoms of an ether, the molecule is … 7/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry slightly polar. Although they have low reactivity overall, the two lone pairs of electrons on the oxygen atom do a ord the ether molecule some reactivity; the ether molecule is subject to reacting with strong acids and serves as a Lewis base. Key Terms alkene: An unsaturated, aliphatic hydrocarbon with one or more carbon–carbon double bond. ester: A compound most often formed by the condensation of an alcohol and an acid, with elimination of water. It contains the functional group C=O joined via carbon to another oxygen atom. ether: Compound containing an oxygen atom bonded to two hydrocarbon groups. amide: Any derivative of an oxoacid in which the hydroxyl group has been replaced with an amino or substituted amino group; especially such derivatives of a carboxylic acid, the carboxamides. Structure of Ethers Ethers are a class of organic compounds that contain an ether group. An ether group is an oxygen atom connected to two alkyl or aryl groups. They follow the general formula R-O-R’. The C-O-C linkage is characterized by bond angles of 104.5 degrees, with the C-O distances being about 140 pm. The oxygen of the ether is more electronegative than the carbons. Thus, the alpha hydrogens are more acidic than in regular hydrocarbon chains. Nomenclature of Ethers There are two ways to name ethers. The most common way is to identify the alkyl groups on either side of the oxygen atom in alphabetical order, then write “ether.” For example, ethyl methyl ether is the ether that has … 8/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry an ethyl group and a methyl group on either side of the oxygen atom. If the two alkyl groups are identical, the ether is called di[alkyl] ether. For example, diethyl ether is the ether with an ethyl group on each Ethers: The general structure of an ether. An ether is characterized by an oxygen bonded to two alkyl or aryl groups, represented here by R and R’. The substituents can be, but do not need to be, the same. side of the oxygen atom. The other way of naming ethers is the formal, IUPAC method. This way, the form is: [short alkyl chain][oxy][long alkyl chain]. For example, the IUPAC name for ethyl methyl ether would be methoxyethane. In cyclic ethers, the stem of the compound is known as a oxacycloalkane. The “oxa” is an indicator of the replacement of the carbon by an oxygen in the ring. An example is oxacyclopentane, a vemembered ring in which there are four carbon atoms and one oxygen atom. Properties of Ethers Ethers are rather nonpolar due to the presence of an alkyl group on either side of the central oxygen. The presence of the bulky alkyl groups that are adjacent to it means that the oxygen atom is largely unable to participate in hydrogen bonding. Ethers, therefore, have lower boiling points compared to alcohols of similar molecular weight. However, as the alkyl chain of the ethers becomes longer, the di erence in boiling points becomes smaller. This is due to the e ect of increased Van der Waals interactions as the number of carbons increases, and therefore the number of Tetrahydrofuran (THF): The common name of the cyclic ether “oxacyclopentane” is tetrahydrofuran, or THF. It is a common organic solvent that is miscible with water. electrons increases as well. The two lone pairs of electrons present on the oxygen atoms make it possible for … 9/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry ethers to form hydrogen bonds with water. Ethers are more polar than alkenes, but not as polar as esters, alcohols or amides of comparable structures. Reactions Ethers have relatively low chemical reactivity, but they are still more reactive than alkanes. Although they resist undergoing hydrolysis, they are often cleaved by acids, which results in the formation of an alkyl halide and an alcohol. Ethers tend to form peroxides in the presence of oxygen or air. The general formula is R-O-O-R’. Ethers can serve as Lewis and Bronsted bases, serving to donate electrons in reactions, or accept protons. Ethers can be formed in the laboratory through the dehydration of alcohols (2R-OH → R-O-R + H2O at high temperature), nucleophilic displacement of alkyl halides by alkoxides (R-ONa + R’-X → R-O-R’ + NaX), or electrophilic addition of alcohols to alkenes (R2C=CR2 + R-OH → R2CH-C(-O-R)-R2). Aldehydes and Ketones Aldehydes and ketones are classes of organic compounds that contain a carbonyl (C=O) group. LEARNING OBJECTIVES Identify the general properties of ketones and aldehydes KEY TAKEAWAYS Key Points The carbonyl functional group is a carbon double bonded to an oxygen. Depending on the location of the carbonyl group, it is termed di erently; ketones contain … 10/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry the carbonyl inside the compound and aldehydes contain the carbonyl at the end of the organic compound. Ketones and aldehydes can undergo keto- enol tautomerism. This refers to the equilibrium between the two possible tautomers. The interconversion of the two forms involves the movement of a proton and the shifting of bonding electrons. This equilibrium a ords the compounds more reactivity. Ketones and aldehydes participate in a variety of reactions. They can undergo oxidation reactions, in which they become oxidized to the corresponding carboxylic acids. Key Terms tautomerism: A form of isomerism in which a dynamic equilibrium between multiple isomers exists, such as that between an enol and a ketone. oxidize: To increase the valence (the positive charge) of an element by removing electrons. aldehyde: An organic compound containing a formyl group, which is a functional group with the structure RCHO. sp2: Hybrid orbital that forms when one pi bond is required for the double bond, and only three σ bonds are formed per carbon atom. The 2s orbital is mixed with only two of the three 2p orbitals. ketone: A compound containing an oxygen atom joined to a carbon atom by a double bond. In organic chemistry, a carbonyl group is a functional group which has a carbon double bonded to an oxygen atom: C=O. … 11/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry Keto-enol tautomers: There exists an equilibrium between the ketone and the enol forms, which involves a shifting of the double bond and the movement of a proton. Ketones When a carbonyl functional group is placed within a molecule, it is known as a ketone. Ketones are organic compounds with the structure RC(=O)R’, where R and R’ can be a variety of carbon-containing substituents. IUPAC nomenclature rules dictate that ketone molecules are named by changing the su x of the parent carbon molecule to “one.” If the position of the ketone must be speci ed, then a number is placed between the parent chain name and the “-one” pre x (e.g., propan-2-one), or at the beginning of the IUPAC name. The pre xes “oxo-” and “keto-” are used to describe the ketone functional group. The ketone carbon is sp2 hybridized, and it adopts a trigonal O planar geometry around the ketonic carbon. As such, the C–C–O and C– C–C bond angles are approximately 120 degrees. Due to the carbonyl group, ketones are polar and are able to interact with other compounds through hydrogen bonding; this hydrogen bond R R' capability makes ketones more soluble in water than related methylene compounds. Ketones are not usually hydrogen bond donors, and they tend not to exhibit Ketone: A ketone is a type of organic compound where a carbonyl group bonds to two other carbon atoms of the carbon backbone. intermolecular attractions with other ketones. As a result, ketones are often more volatile than alcohols and carboxylic acids of comparable molecular weights. Ketones have alpha - … 12/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry hydrogens which participate in keto-enol tautomerism. In the presence of a strong base, enolate formation and subsequent deprotonation of the enolate will occur. Aldehydes An aldehyde is an organic compound that contains a carbonyl group with the central carbon bonded to a hydrogen and R group (R-CHO). Aldehydes di er from ketones in that the carbonyl is placed at the end of the carbon skeleton rather than between two carbon atoms of the backbone. Like ketones, aldehydes are sp2 Aldehyde: An aldehyde is characterized by the presence of a carbonyl functional group at the end of a compound’s carbon skeleton. hybridized and can exist in the keto or enol tautomer. Aldehydes are named by dropping the su x of the parent molecule, and adding the su x “-al.” For instance, a threecarbon chain with an aldehyde group on a terminal carbon would be propanal. If there are higher order functional groups on the compound, the pre x “oxo-” can be used to indicate which carbon atom is part of the aldehyde group. If the location of the aldehyde must be speci ed, a number can be used in between the parent chain and su x, or at the beginning of the compound name. Similarities of Aldehydes and Ketones Both aldehydes and ketones exist in an equilibrium with their enol forms; the enol form is de ned as an alkene with a hydroxyl group a xed to one of the carbon atoms composing the double bond. The keto form predominates at equilibrium for most ketones. However, the enol form is important for some reactions because the deprotonated enolate form is a strong nucleophile. The equilibrium is strongly thermodynamically driven, and at room temperature the keto form is favored. The interconversion can be catalyzed by the presence of either an acid or a base. … 13/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry Overall reaction: OH R R' R R' O Reaction mechanism H O + H OH R H R' R O R' H H H R' R O O H Acid catalyzed enolization O H H H R' R O R H H O R' R' O R OH H Base catalyzed enolization H R' H R' R O R' H H O R O O H R OH Keto-enol tautomerism: The interconversion between the two forms can be catalyzed by an acid or a base. Ketone and Aldehyde Spectroscopy Both ketones and aldehydes can be identi ed by spectroscopic methods. They display strong CO absorption bands near 1700 cm-1. In NMR spectroscopy, the carbonyl hydrogen shows a strong absorption peak, and any coupling to protons on the alpha carbon will also show strong signals. Ketones and aldehydes can both be readily reduced to alcohols, usually in the presence of a strong reducing agent such as sodium borohydride. In the presence of strong oxidizing agents, they can be oxidized to carboxylic acids. As electrophiles, they are subject to attack by nucleophiles, meaning they participate in many nucleophilic addition reactions. … 14/26 10/27/2019 Functional Group Names, Properties, and Reactions | Boundless Chemistry Carboxylic Acids Carboxylic acids are organic acids that contain a carbon atom that participates in both a hydroxyl and a carbonyl functional group. LEARNING OBJECTIVES Recognize the general properties of carboxylic acids KEY TAKEAWAYS Key Points Carboxylic acids are used as precursors to form other compounds such as esters, aldehydes, and ketones. Carboxylic acids can exhibit hydrogen bonding with themselves, especially in non- polar solvents; this leads to increased sta...
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