Comparison of boiling points of Butanoic acid PDF

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Comparison of boiling points of Butanoic acid, Pentanoic acid, 2-methylpropanoic acid, 2-hexanone. Average grade...

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Comparison of boiling points of Butanoic acid, Pentanoic acid, 2-methylpropanoic acid, 2hexanone.

Table 1.1: Boiling points of pentaoic acid, butanic acid, 2-methylpropaoic acid and 2hexanone Compound

Boiling point

Pentaoic Acid (C5H10O2)

186-187oC

Functional group Carboxylic Acid

Butanic Acid (C4H8O2)

163.5oC

Carboxylic Acid

2-methylpropaoic 152-155oC acid (C4H8O2)

2-hexanone (C6H12O0)

127oC

Structure

Carboxylic Acid

Ketone

Table 1.1: Pentaoic acid; (Forth, 1888), Butanic Acid; (The Merk Index), 2-methylpropaoic acid; (Lippincott and Hass, 1939), 2-hexanone; (Colman and Perkin, 1889). As outlined in the table above Pentaoic acid has the highest boiling point of 186oC followed by Butanic acid 163.5oC, 2-methylpropaoic acid 155oC and 2-hexanone 127.6oC having the lowest. The boiling point of these compounds are linked to each of their molecular weight, functional groups and intermolecular forces. The boiling point of a compound is defined as the point at which the vapor pressure of a liquids meets equilibrium with its external environment creating gas. (Helmenstine, Anne Marie, Ph.D). A compounds weight and intermolecular forces also directly effect a compounds boiling point. As a compounds molecular weight and intermolecular forces increase so does the compounds boiling point. The intermolecular forces are the attraction between the molecules within a compound, these are also strongly related to the physical properties of a compound (Reed, Curtiss and Weinhold, 1988) Pentaoic acid has the highest boiling point of 186oC as shown in table 1.1. Pentanoic acid, is a straight chain compound with a carboxylic acid functional group, its chemical formula is C5H10O2 (Shaw, 2010) Pentaoic acid has the highest boiling point due to its longer carbon chain compared to the other carboxylic acids in table 1.1. Pentaoic acid like all carboxylic

acids are held together with hydrogen bonds between its atoms, Hydrogen bonding is the strongest of the intermolecular forces and thus require more energy to break (Bishop, 2018). Butanic acid’s boiling point is 163.5oC with a chemical formula of C4H8O2. Like Pentaoic acid is also a carboxylic acid but due to its slightly shorter carbon chain its boiling point is lower than pentaoic acids. Again, like all carboxylic acids butanic acid exhibits hydrogen bonding within its molecules. 2-methylpropaoic (C4H8O2) acid has the lowest boiling point compared to the other carboxylic acids in table 1.1. This is because of its methyl group on the second carbon in its chain. This methyl group causes the lower boiling point of this carboxylic acid due to the methyl group creating a weaker van der waals reaction. Van der waals reactions are the weakest of the intermolecular forces a Van der waal reaction is the attraction and repulsion of atoms within molecules in relation to other intermolecular forces (Balakrishnan, 2004). Due to the smaller reduce contact between molecules in the chain there is less energy required to break the compounds intermolecular forces giving it a lower boiling point compared to the other carboxylic acids. 2-hexanone has the lowest boiling point of 127.6oC, shown in table 1.1. Although 2hexanone has a longer carbon chain than any of the carboxylic acids in table 1.1 its functional ketone group gives it a lower boiling point. A Ketone is a carbon with a double bonded oxygen attached the location of the ketone is identified in the chain by the lowest number possible (Damayanti and Ikhsan, 2017). A ketone lacks the hydroxyl group apparent within a carboxylic acid opting instead for a double bonded oxygen on its carbon chain(C=O). This polar bond between the carbon and oxygen allows for a dipole-dipole reaction. A dipole-dipole reaction occurs a negative portion of a molecules is attracted to the positive of another (Nicholls, 1983) creating a dipole-dipole bond. Although a dipole-dipole is stable and contributes to a higher boiling point it is not as strong as hydrogen bonding expressed in table 1.1, whereas the carboxylic acids still have higher boiling points. A compounds weight, functional group and intermolecular forces directly effects its boiling point. A compound with a longer carbon chain will have a higher molecular weight and will require more energy to break creating higher boiling points than a compound with a shorter carbon chain. A compounds functional group will also directly affect a compounds boiling point this is because different functional groups exhibit different intermolecular forces. As displayed in table 1.1 all carboxylic acids exhibit hydrogen bonding as their intermolecular forces. Hydrogen bonding is the strongest form of bonding and thus requires higher amounts of energy to break meaning that carboxylic acids have higher boiling points compared to ketones which exhibit a Dipole-Dipole bond. Adding groups to compounds, especially carboxylic acids. Reduce the compounds boiling point as shown in table 1.1 butanic acid and 2-methylpropoic acid are both very similar but 2-methylpropic has a lower boiling point. This is because the methyl group reduces the strength of the molecular bonds in its carbon chain and creates a Van der waals reactions which is the weakest form of a molecular bond. These bonds are only temporary. Finally, 2-hexanone has the lowest boiling point even thought it has the longest carbon chain. This is because 2-hexanone has a ketone as its function group.

A ketone has a polar bond between its carbon chain and an oxygen molecule this is called a dipole-dipole reaction. In conclusion, as shown by table 1.1. Pentaoic acid (C5H10O2) has the highest boiling point of 186-187oC due to its longer carbon chain and its strong intermolecular forces. Buatnic Acid (C4H8O2) although similar to pentaoic acid in its intermolecular bonding through hydrogen bonding has the second highest boiling point due to its shorter carbon chain compared to pentaoic acid. 2-methylpropaoic acid (C6H12O0) has the third highest boiling point compared to the other carboxylic acids in table 1.1 due to its methyl group. This methyl group creates a van der waals reaction, which is the weakest intermolecular force. In its carbon chain meaning less energy is required to break its bonds. Finally, 2-hexanone (C6H12O0) has the lowest boiling point in table 1.1. 2-hexanone although having the longest carbon chain has the lowest boiling point because of its ketone function group. A ketone exhibits a dipoledipole bond which is a polar bond between two molecules that is stronger than a van der waals reactions but not as strong as hydrogen bonding.

References

Bishop, M. (2018). Attractions and Boiling. [online] Preparatorychemistry.com. Available at: http://preparatorychemistry.com/Bishop_attraction_strengths.htm [Accessed 3 Oct. 2018]. Helmenstine, Anne Marie, Ph.D. (2018, June 22). Boiling Point Definition in Chemistry.

Reed, A., Curtiss, L. and Weinhold, F. (1988). Intermolecular interactions from a natural bond orbital, donor-acceptor viewpoint. [online] 88(6), pp.899-926. Available at: [Accessed 2 Oct. 2018]. Shaw, W. (2010). Increased urinary excretion of a 3-(3-hydroxyphenyl)-3-hydroxypropionic acid (HPHPA), an abnormal phenylalanine metabolite ofClostridiaspp. in the gastrointestinal tract, in urine samples from patients with autism and schizophrenia. Nutritional Neuroscience, 13(3), pp.135-143. Damayanti, L. and Ikhsan, J. (2017). Development of monograph titled “augmented chemistry aldehida & keton” with 3 dimensional (3D) illustration as a supplement book on chemistry learning. [online] Available at: http://apps.webofknowledge.com.ezproxy.uws.edu.au/full_record.do? product=WOS&search_mode=GeneralSearch&qid=1&SID=D3PTJlzWz1fOaSfxEJn&page=1&d oc=6 [Accessed 3 Oct. 2018]. Forth, E. (1888). ber die Darstellung von Normalvalerian- und Dipropylessigs�ure aus Malons�ure�thylester und die L�slichkeit einiger Salze derselben. Monatshefte f�r Chemie, [online] 9(1), pp.308-322. Available at: https://www-rscorg.ezproxy.uws.edu.au/Merck-Index/monograph/m11360/valeric%20acid?q=authorize [Accessed 3 Oct. 2018]. Www-rsc-org.ezproxy.uws.edu.au. (2018). WSU Library - EzProxy. [online] Available at: https://www-rsc-org.ezproxy.uws.edu.au/Merck-Index/monograph/m2867/butyric%20acid? q=authorize [Accessed 3 Oct. 2018]. Lippincott, S. and Hass, H. (1939). Action of Mineral Acids on Primary Nitroparaffins. Industrial & Engineering Chemistry, [online] 31(1), pp.118-120. Available at: https://www-rsc-org.ezproxy.uws.edu.au/Merck-Index/monograph/m6470/isobutyric %20acid?q=authorize [Accessed 3 Oct. 2018]. Colman, H. and Perkin, W. (1889). XXXVIII.—Acetopropyl alcohol and acetobutyl alcohol. J. Chem. Soc., Trans., 55(0), pp.352-359. Nicholls, L. (1983). A demonstration of dipole-dipole interactions. Journal of Chemical Education, 60(11), p.993. Balakrishnan, N. (2004). On the role of van der Waals interaction in chemical reactions at low temperatures. The Journal of Chemical Physics, 121(12), pp.5563-5566....