Hydroxyl Group

8 Key excerpts on "Hydroxyl Group"

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  eBook - ePub

  Principles of Organic Chemistry

  • Robert J. Ouellette, J. David Rawn(Authors)
  • 2015(Publication Date)
  • Elsevier

    (Publisher)

  8

  Alcohols and Phenols

  8.1 The Hydroxyl Group

  Families of organic compounds that have functional groups containing oxygen include alcohols, phenols, ethers, aldehydes, ketones, acids, esters, and amides. Alcohols and phenols both contain a Hydroxyl Group (–OH). A Hydroxyl Group is also present in carboxylic acids, but it is bonded to a carbonyl carbon atom. As a result, the chemistry of carboxylic acids, the subject of Chapter 12 , is substantially different from the chemistry of alcohols and phenols. Alcohols and phenols can be viewed as organic “relatives” of water in which one hydrogen atom is replaced by an alkyl group or an aryl group. Alcohols contain a Hydroxyl Group bonded to an sp3 -hybridized carbon atom. Phenols have a Hydroxyl Group bonded to an sp2 -hybridized carbon atom of an aromatic ring.

  Common Names of Alcohols

  The common names of alcohols consist of the name of the alkyl group (Section 3.3 ) followed by the term alcohol . For example, CH3 CH2 OH is ethyl alcohol and CH3 CH(OH)CH3 is isopropyl alcohol. Other common names are allyl alcohol and benzyl alcohol, whose structures are shown below.

  The IUPAC system of naming alcohols is based on the longest chain of carbon atoms that includes the Hydroxyl Group as the parent chain. The parent name is obtained by substituting the suffix -ol for the final -e of the corresponding alkane. The IUPAC rules are as follows:

  1.  

  The position of the Hydroxyl Group is indicated by the number of the carbon atom to which it is attached. The chain is numbered so that the carbon atom bearing the Hydroxyl Group has the lower number.

  The longest chain that contains the Hydroxyl Group has 4 carbon atoms. An OH group is at C-2 and a methyl group is at C-3. So, the name is 3-methyl-2-butanol

  2.  

  When the Hydroxyl Group is attached to a ring, the ring is numbered starting with the carbon atom bearing the Hydroxyl Group. Numbering continues in the direction that gives the lowest numbers to carbon atoms with substituents such as alkyl groups. The number 1 is not used in the name to indicate the position of the Hydroxyl Group.

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  eBook - ePub

  Pharmaceutical Chemistry E-Book

  • David G. Watson(Author)
  • 2011(Publication Date)
  • Churchill Livingstone

    (Publisher)

  Chapter 5 Oxygen- and sulphur-containing functional groups

  David G. Watson

  Chapter contents

  Introduction 77

  Monohydric alcohols 78

  Ethanol 78

  Other aliphatic alcohols 79

  Benzyl alcohol 79

  Diols and triols 79

  Polyols 80

  Some chemical properties of alcohols 81

  Loss of water 81

  Oxidation 81

  Phenols 81

  Esterification 86

  Ethers 88

  Aldehydes and ketones 89

  Carboxylic acids 91

  Salts of carboxylic acids 93

  Salts formed between amines and carboxylic acids 94

  Esters 94

  Chemical stability 95

  Enzymatic hydrolysis of esters 97

  The role of esters in modifying physicochemical properties of drugs 101

  Esters for improving drug absorption 101

  Esters for improving water solubility 102

  Esters used for sustained drug delivery 103

  Esters for improving drug acceptability and reducing side effects 103

  The role of esters in terminating drug action 105

  Participation of the ester group in drug action 105

  The ester linkage in polymeric drugs 107

  Esters in biological systems 108

  Phosphate esters in biology 108

  Introduction

  Oxygen in the most electronegative element found in biomolecules since fluorine does not occur naturally in biological compounds. Its high affinity for electrons means that unlike nitrogen it does not share its lone pairs with protons readily. Thus oxygen-containing groups tend to be less potent in conferring pharmacological activity. For example, dopamine differs from noradrenaline by lacking a Hydroxyl Group but they both have potent effects on the heart: remove the amine group and activity is totally abolished. This is really a generalisation, it is probably truer to say that where oxygen-containing groups play an important role in conferring pharmacological activity they have a very specifically targeted function. In contrast, the charged nitrogen atom exerts a more general effect and may affect a number of targets. This theme will be expanded later in the chapter. Water is the fundamental oxygen-containing biologically active substance and some of its unique properties have been discussed in Chapter 1

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  Introduction to Genomic Signal Processing with Control

  • Aniruddha Datta, Edward R. Dougherty(Authors)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  2.2 Some Chemical Bonds and Groups Commonly En-countered in Biological Molecules C-H Compounds Compounds containing only carbon and hydrogen are called hydrocarbons . Examples are methane ( CH 4 ) and ethane ( C 2 H 6 ), which have the structures shown below. C H H H H Methane C H H H Methyl Group C C H H H H H C C H H H H H H Ethane Ethyl Group By removing one of the hydrogen atoms from methane, we obtain a highly reactive group called the methyl group . The ethyl group is similarly derived from ethane. C − O Compounds We next consider organic compounds that contain carbon and oxygen in addition to other elements. There are different classes of compounds that fall into this category. Alcohols are characterized by the presence of the hydroxyl (OH) group and have the general formula R − OH. Here R could be any organic group. When R = CH 3 , i.e. the methyl group, the corresponding alcohol is called methyl alcohol or methanol . When R = C 2 H 5 i.e. the ethyl group, the corresponding alcohol is called ethyl alcohol or ethanol . Aldehydes are characterized by the general formula 10 Introduction to Genomic Signal Processing with Control C H R O where R is any organic group. When R = H , the corresponding aldehyde is called formaldehyde and when R = CH 3 , the corresponding aldehyde is called acetaldehyde . Ketones are characterized by the general formula C R 2 O R 1 where R 1 and R 2 can be any two organic groups. The C = O (C double bonded with O) is called the carbonyl group and it is present in both aldehydes and ketones. Carboxylic Acids are characterized by the general formula C OH R O where R is any organic group. When R = H , the corresponding acid is called formic Acid while when R = CH 3 , the corresponding acid is called acetic Acid . The COOH group present in all carboxylic acids is called a carboxyl group.

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  eBook - PDF

  Organic and Biological Chemistry

  • H. Stephen Stoker(Author)
  • 2015(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  hydroxide group b. Hydroxyl Group c. hydroxide ion d. no correct response 2. The simplest alcohol possible contains how many hydrogen and oxygen atoms, respectively? a. 1 and 1 b. 2 and 1 c. 4 and 1 d. no correct response 3. Which of the following statements concerning alcohols in incorrect ? a. They may be viewed as alkyl or cycloalkyl derivatives of water. b. They may be viewed as hydroxyl derivatives of alkanes or cycloalkanes. c. The functional group is always attached to a saturated carbon atom. d. no correct response Section 3-2 Quick Quiz Answers: 1. b; 2. c; 3. d 3-3 Nomenclature for Alcohols L E A R N I N G F O C U S Given their structural formulas, be able to name alcohols using IUPAC rules or vice versa; know common names for alcohols with simple alkyl or cycloalkyl groups. Common names exist for alcohols with simple (generally C 1 through C 4 ) alkyl groups. A common name is assigned using the following rules: Rule 1: Name all of the carbon atoms of the molecule as a single alkyl group. Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 84 CHAPTER 3 Alcohols, Phenols, and Ethers Rule 2: Add the word alcohol, separating the words with a space. CH 3 CH 3 CH 2 O O O CH 3 CH 2 O CH 2 O O Ethyl alcohol Methyl alcohol Propyl alcohol OH OH OH OH OH CH 3 CH 3 CH O O A Isopropyl alcohol Cyclobutyl alcohol OH OH IUPAC rules for naming alcohols that contain a single Hydroxyl Group are: Rule 1: Name the longest carbon chain to which the Hydroxyl Group is attached. The chain name is obtained by dropping the final -e from the alkane name and adding the suffix -ol.

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  eBook - PDF

  Biochemistry

  An Integrative Approach

  • John T. Tansey(Author)
  • 2019(Publication Date)
  • Wiley

    (Publisher)

  Likewise, if a functional group does not behave as expected, the hypothesis needs to be re-examined, and theories or understanding of the system may need to change. Many of the common functional groups found in biochemistry will be familiar (Table 1.2). They include Hydroxyl Groups, carbonyl groups, amines, and carboxylic acids. Others, such as thiols and phosphates may be less familiar. These groups combine to generate more complex molecules such as amides and disulfides. Many of the molecules studied in biochemistry were identified before systematic methods of nomenclature were adopted, and therefore they have common names. Other molecules use the older Greek lettering system instead of numbering to identify the location of functional groups in a molecule (Figure 1.6). Although this is not the International Union of Pure and Applied Chemistry (IUPAC) nomenclature system that is used in organic chemistry, dissect- ing the name of a molecule can still help provide clues to its structure and function. For exam- ple, as the name implies, α-ketoglutarate contains a carbonyl group (keto) α to a carboxylate (ending in the suffix “-ate”). Without knowing other information, such as the structure of Fatty acid δ γ β α O 4 3 2 1 5 O - α-ketoglutarate α 1 2 O O O O - - O FIGURE 1.6 Organic nomen- clature using the Greek letter- ing system. In α-ketoglutarate the carbonyl (keto) group is α to the higher priority carboxyl group. Fatty acids are broken down through a process termed β-oxidation. The oxidation occurs on the β-carbon. 12 CHAPTER 1 The Chemical Foundations of Biochemistry glutarate, it is not possible to draw out the full structure, but the name still provides a guide. Likewise, fatty acids are broken down through a process termed β-oxidation. In this example, the oxidation occurs at the β-carbon. 1.2.2 The solubility and polarity of a molecule can be determined from its structure All biochemistry occurs in aqueous systems.

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  eBook - PDF

  Oxidation and Antioxidants in Organic Chemistry and Biology

  • Evgeny T. Denisov, Igor B. Afanas'ev(Authors)
  • 2005(Publication Date)
  • CRC Press

    (Publisher)

  7 Oxidation of Alcohols and Ethers 7.1 OXIDATION OF ALCOHOLS 7.1.1 I NTRODUCTION The Hydroxyl Group of alcohol weakens the a -C H bond. Therefore, free radicals attack preferentially the a -C H bonds of the secondary and primary alcohols. The values of bond dissociation energy (BDE) of C H bonds in alcohols are presented in Table 7.1. The BDE values of C H bonds of the parent hydrocarbons are also presented. It is seen from comparison that the Hydroxyl Group weakens BDE of the C H bond by 23.4 kJ mol 1 for aliphatic alcohols and by 8.0 kJ mol 1 for allyl and benzyl alcohols. Alcohols are polar compounds. They have dipole moment and this influences their reactivity in reactions with polar peroxyl radicals (see later). The values of the dipole moments m for selected alcohols are given below [6]. Alcohol MeOH EtOH Me 2 CHOH PhCH 2 OH CH 2 ¼¼ CHCH 2 OH m (Debye) 1.70 1.69 1.58 1.71 1.60 Alcohols having a Hydroxyl Group form hydrogen bonds with polar compounds such as hydroperoxides, ketones, etc. This causes some peculiarities of the oxidation kinetics of alcohols. On the other hand, alcohols are weak acids and dissociate as acids in polar alcoholic media. Protonated alcohol molecules induce several heterolytic and homolytic reactions complicating the mechanism of oxidation and composition of the products. The Hydroxyl Group of the alkyl radical formed from alcohol complicates the mechanism of alcohol oxidation also. One of the peculiarities of alcohol oxidation is the production of hydrogen peroxide as a primary intermediate, and another is a high reducing activity of peroxyl radicals formed from oxidized alcohols. The chemistry and kinetics of alcohol oxidation are discussed in detail in monographs [7–10]. 7.1.2 C HAIN M ECHANISM OF A LCOHOL O XIDATION Alcohols, like hydrocarbons, are oxidized by the chain mechanism. The composition of the molecular products of oxidation indicates that oxidation involves first the alcohol group and the neighboring C H bond.

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  eBook - ePub

  Organic Chemistry

  Concepts and Applications

  • Allan D. Headley(Author)
  • 2019(Publication Date)
  • Wiley

    (Publisher)

  3 Heteroatomic Functional Groups and Organic Nomenclature

  3.1 Properties and Structure of Alcohols, Phenols, and Thiols

  Alcohols have the ─OH functional group, and alcohols are very important compounds in organic chemistry and today’s economy. Alcohols that have three or less carbons are some of the most common alcohols. Methanol, which has one carbon, is often used as an alternate fuel for the internal combustion engines. It is a desirable alternative fuel since its combustion is very efficient. It is typically combined directly with gasoline but can be used directly as is the case with some racing cars. Methanol can typically be oxidized to form formaldehyde and formic acid, which are compounds that are used widely in industry. Ethanol has two carbons and is also used as a blend in combination with gasoline for fuel. It is also the alcohol of alcoholic beverages. Since pure ethanol is a strong dehydrating agent, it cannot be consumed directly. Alcoholic liquids, such as whiskey, are mixtures of ethanol and water, and the typical mixture is in the range of 45–50% in ethanol/water by volume. The term proof is an old terminology, which refers to the alcoholic content of an alcoholic mixture and is defined as twice the percentage of alcohol by volume; thus, for example, a 50% alcohol solution, is also referred to as 100 proof. A major health disadvantage in the use of ethanol is that it is oxidized rapidly and can result in cirrhosis of the liver. On the other hand, methanol, which has a very similar structure to ethanol, is toxic to the body; it damages the optic nerve, which results in blindness, so it should never be consumed. Ethylene glycol, another alcohol that has two ─OH groups, is the main component of antifreeze/coolant. Owing to the low vapor pressure, very high boiling point (197 °C), and very low freezing point (−13 °C) of ethylene glycol, it remains a liquid even in the most severe winter and summer weather. Interestingly, propylene glycol, another alcohol that has two ─OH groups, is used in small amounts in the food and cosmetic industries, whereas ethylene glycol is poisonous. Another important alcohol is isopropanol, which is also known as rubbing alcohol. Isopropanol has many household and personal care uses, and it is also used in industry as a solvent.

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  eBook - ePub

  Chemistry for Pharmacy Students

  General, Organic and Natural Product Chemistry

  • Lutfun Nahar, Satyajit Sarker, Professor Satyajit D. Sarker(Authors)
  • 2019(Publication Date)
  • Wiley

    (Publisher)

  Hofmann rearrangement.

  4.4 CARBONYL COMPOUNDS

  Carbonyl compounds are molecules that contain a carbonyl functional group (C═O), which is a carbon double‐bonded to an oxygen atom. An acyl functional group (R─C═O) consists of a carbonyl group attached to an alkyl or an aryl group. A carbonyl group containing compounds can be classified into two broad classes: one group includes compounds that have hydrogen and carbon atoms bonded to the carbonyl carbon, and the other group contains an electronegative atom such as oxygen, chloride and nitrogen bonded to the carbonyl carbon (see Section 4.4.2.9 ). The carbonyl group is of central importance in organic chemistry because of its abundance. Numerous reactions with aldehydes, ketones, carboxylic acids, esters, acid chlorides and amides have been shown earlier (see Sections 4.3.4.4 , 4.3.4.7 and 4.3.8.7 ).

  4.4.1 Aldehydes and Ketones

  Aldehydes have an acyl group with a hydrogen atom bonded to the carbonyl carbon. The most abundant natural aldehyde is glucose. The simplest aldehyde is formaldehyde (CH2 O), where the carbonyl carbon is bonded to two hydrogen atoms. In all other aldehydes, the carbonyl carbon is bonded to one hydrogen atom and one alkyl or aryl group; for example, acetaldehyde (CH3 CHO) and benzaldehyde (Ph─CHO). Many aldehydes have distinctive strong odours. Benzaldehyde smells like cherries and is found naturally in many fruits such as peaches, grapes and cranberries. It is used as an artificial flavouring in many foods at low levels, but is toxic at higher levels.

  Ketones have an acyl group with another alkyl or aryl group connected to the carbonyl carbon. The simplest ketone is acetone (CH3 COCH3 ), where the carbonyl carbon is bonded to two methyl groups. Acetone and methyl ethyl ketone (MEK

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