Alcohols, Aldehydes and Ketones, Amines and Amides, Carboxylic Acids, Ethers - Case Study Example

Student’s Name: Professor’s Name: Course Title: Date: Functional Groups Functional groups refer to portions of a molecule that are classified/recognizable group of bound atoms (Jim, 2004). It is generally common in organic chemistry to encounter molecules that comprises mainly of carbon structure with various functional groups being attached to the carbon chain. Regardless of the molecule containing the functional group, its unique chemical properties are given by the functional group thereby influencing their chemical reactivity. There are various functional groups for instance alkenes, benzene ring, sulfide, alcohol, alkyne, alkyl halide, ketone, ether, aldehyde, carboxylic acid, amines, ester, amide, nitrile, acid chroline and imines among others (ChemEd DL). This research essay takes a closer look at the basic structures, examples, physical and chemical properties of common functional groups. Alcohols Alcoholic molecules has at least one hydroxyl group of molecules (OH groups) which is substituted for hydrogen atoms on the carbon chain. A common example of an alcohol molecule is ethanol and the general molecular formula of alcohols is of the form CH3CH2OH which translates into the below structural formula. Figure 1. Structural formula of ethanol Physical properties Most of the common alcohols are colourless liquids at room temperature. Alcohols with four to ten carbon atoms are usually viscous and heavier as compared to those with at least twelve carbon atoms which are generally solid at room temperature. The hydrogen bonding between water and alcohols renders solubility of alcohols in water to decreases proportionately with length of the carbon chain (Reusch). On the other hand, alcohols have high boiling points which are attributed to hydrogen bonding the stronger bonds formed require more energy to break hence the higher boiling points. Comparison between alcohols and ethers of the same molecular weight shows a considerably higher boiling point in alcohols. An example is comparison between ethanol and dimethyl ether, its constitutional isomer (Smith and March 687). Common Chemical Reactions Oxidation –The manner in which alcohol withstands oxidation depends on its structure. Basiclally, primary alcohols can be oxidized to aldehydes by the removal of H2 as illustrated below. Consequently, a secondary alcohol can be oxidized to a ketone by the removal of H2 as follows. However, tertiary alcohols are resistant to oxidation because of the absence of hydrogen atoms on the carbon attached to the –OH group. This is illustrated below. Substitution –This result in synthesis of Alkyl halides, it is done by effectively substituting a halogen atom for the hydroxyl group. Upon being reacted with Hydrochloric, hydrobromic and hydroiodic acids, tertiary alcohols give the best results in for substitution (Reusch). Esterification –This refers to reaction between alcohols and carboxylic acids which results in formation of esters. Esterification happens when alcohols are heated together with carboxylic acids whilst the reaction is activated with an acid-based catalyst. The reaction is slow and reversible. Making of ethane ethanoate from ethanoic acid and ethanol is illustrated below. (Reusch) Aldehydes and Ketones An aldehyde is an organic compound in which its structural formula there is a double bond between an oxygen atom and a carbon atom in addition to a single bond a hydrogen atom as well as other(s) atoms. Ketones are characterized by carbonyl groups whereby there is a covalent bond between an oxygen atom and a carbon atom. The outstanding double bonds links to other hydrocarbon radicals or carbon atoms (Carey and Sudberg 450). In this context, a example of aldehyde is for instance Butanol with the following structural formula. Conversely, an example of ketone is for instance acetone which has the below structural formula. Physical Properties Aldehydes and Ketones are polar molecules because the C=O bond has a polar moment. This renders their boiling points to be higher compared to alkenes of the same molecular weight. As these ketones do not donate hydrogen bonds, they therefore have lower boiling points as compared to alcohols of similar molecular weights. The fact that they are hydrogen bond accepters gives them considerable solubility in water. Some aldehydes have a fruity aroma while others have more acrid odour, Ketones usually have the distinctive smell of acetone with varying degrees of mildness (Seager and Slabaugh 413). Common Chemical Reactions Oxidation –Owing to the absence of the hydrogen atom attached to the Carbon – Oxygen double bond in Ketones, they are not as easy to oxidize as aldehydes; only very strong oxidizing agents oxidize ketones. They do this by breaking Carbon-Carbon bonds which is destructive and can therefore not be pursued in terms of by products from the reaction. Aldehydes are easily oxidized by different oxidizing agents (ChemEd DL). In case aldehydes are oxidized in acidic or alkaline conditions, they either form carboxylic acids or salts respectively as illustrated below. Under acidic conditions, the reaction can be represented as: Under under basic conditions it may be represented as: Carbonyl compounds takes on the role of an oxidizing agent whereas hydrogen gas acts as a reducing agent in presence of metal-based. It is important to note that other types of reducing agents that lead to production of hydrogen can be used in such a reaction. Reduction –Reduction in aldehydes and ketons happens, mostly with the use of lithium tetrahydridoaluminate and sodium tetrahydridoborate. In aldehyde it produces primary alcohols, in ketones it produces secondary alcohols it is a nucleophilic addition (Carey and Sudberg 498). Amines and Amides Amines and amides contain two Nitrogen atoms attached to their carbon chains and below is the basic structural of them both. Amine Amide Physical Properties Boiling /Melting Points –primary and secondary amines have a little bit lower boiling points as compared to alcohols with similar molecular weight. This is because the H-bond of N-H is not as robust as H-bond of the O-H. Tertiary amines on the other hand do not make a H-bond with each other and therefore their boiling points are similar to those of other hydrocarbons with similar molecular weights. Most amides are solids except methanamide which is a liquid at room temperature (Smith and March 121). Water solubility –Primary amines are soluble in water because as they readily make H-bond with water. Tertiary amines that do not form H-bond are soluble based on the fact that they readily form H-bonds with water molecules by making use of nitrogen. Water solubility reduces as the carbon chains become longer. Subsequently, small amines are capable of forming H-bonds with water molecules leading them to be highly soluble in water. Hydrogen bonds between water molecules and between amide molecules have to be broken in order for amides to dissolve in water before water and amides can mix, this requires energy (Boudreaux ). Odour –Lower molecular weight amines have putrid odours, with increasing size, they become less volatile and the odour decreases eventually becoming unnoticeable (Smith and March 125) Common Chemical Reactions Hydrolysis –In this reaction amides are converted to acids and amines, the reaction is slow in the absence of a catalyst (Carey and Sudberg 617). The Hinsberg Test –Benzenesulfonyl chloride reacts chemically with amines in a way that distinguishes between primary, secondary and tertiary amines. Primary and secondary amines react with it to result in sulfonamide derivatives, whereas tertiary amines do not result in formation of any isolable products apart from amine. In the last reaction, a quaternary salt can be result as an intermediate product although it rapidly breaks down in the presence of water to form the original tertiary amine. Amines are reacted with acids, to form ammonium salts (Carey and Sudberg 618). Carboxylic Acids These are distinguished from other organic compounds by the fact that they are acidic. This functional group is made up of a hydroxyl group bonded to a carbonyl group. The general formula of carboxylic acid is R-COOH and common molecules are for instance methanoic acid, ethanoic acid, propanoic acid and 2-methylbutanoic acids with the following structural formulae (Jim 2003). Structural formula of common carboxylic acids Physical Properties Boiling Points –Boiling points of carboxylic acid are higher than that of alcohols of identical molecular mass and similar number of electrons. This is because hydrogen bonding occurs between two acid molecules leading to formation of dimer thereby leading to increased size of molecule and thus increased boiling point (Reusch). Water Solubility –in instances where carboxylic acids have up to a maximum of 4 C-atoms, they solubilise well with water. This changes as the acid molecules become bigger and its attributable to the fact that the bigger acids have tend to have long hydrocarbon molecular chain that gets between water molecules leading to breakage of hydrogen bonds. The broken bonds can only be substituted with weak Van der Waals forces of dispersion. Some of acid’s molecules react with water instead of dissolving in it further hindering solubility. Carboxylic acids have very foul odours e.g. butanoic acid which is the main ingredient of stale sweat (Reusch) Esters Esters are derivatives of carboxylic acids in which the hydrogen in the carboxylic acid group is replaced with a hydrocarbon. Fats and oils form are generally esters but a common example of an ester is ethyl ethanoate with its structural molecule as illustrated below.. Physical Properties of Esters Boiling Point –Although Ester have a polar carbonyl, they do not have a hydrogen atom to facilitate hydrogen bonding. Thus, esters have a low boiling points compared to majority of molecules of same the same size and sometimes even when the other molecules are bigger esters still have lower boiling points (Patai 165). Water Solubility –Small esters are soluble in water; solubility reduces with the increase in length of the chain. The smaller esters are able to dissolve because even if ester molecules cannot hydrogen bond with each other and they are capable of forming bonds with water molecules.. The most distinctive attribute of esters is their sweet fruity aroma (Patai 166). Ethers Ethers are a group of organic compounds in whereby an oxygen atom is bonded to two alkyl or aryl groups. When compared to alcohol, ethers have lower boiling points, and are less soluble in water. They are pleasant smelling. An example of ether molecule is dimethyl ether Common Chemical reactions of Ester and Ethers Similarly to carboxylic acids, out of which esters are derived when reacted with lithium alluminiumhydrades, esters form primary alcohols. Conversely, autoxidation is a common ether reaction. This occurs in the presence of oxygen whereby ethers oxidize to form hydro peroxides and dialkyl peroxides. These peroxides may explode when heated and it is for such reason that ethers should be obtained in small quantities and used quickly (Patai 167). Works Cited Boudreaux, Kevin A. “Amines and Amides.” Angelo State University. n.d. ppt. Carey, F.A. and Sudberg, R.A. Advanced Organic Chemistry, 5th Ed. Springer, 2007. Print. ChemEd DL. Properties of Organic Compounds and Other Covalent Substances. Chemical education digital library. 23 Aug 2009. Web. 4 Aug. 2012. < http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Properties-of-Organic-Compounds-and-Other-Covalent-Substances-522.html>. Jim, Clark. Introduction to alcohols. Chemguide, 2003. Web. 4 Aug. 2012. < http://www.chemguide.co.uk/organicprops/alcohols/background.html>. ------------. Introduction to carboxylic acids. Chemguide, 2004. Web. 5 Aug. 2012. < http://www.chemguide.co.uk/organicprops/acids/background.html#top>. Patai, S. The Chemistry of Ether Linkage. Wiley, 1967. Print. Reusch, William. Functional group reactions. Department of Chemistry, Michigan State University, East Lansing, MI. 2 June 2010. Web. 4 Aug. 2012. < http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htm>. Smith, M. B. and March, J. March’s Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 6th edition. Wiley, 2007. Print. Read More