Bonded to the hydroxyl primary only 1 carbon

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bonded to the hydroxyl: Primary – only 1 carbon, Secondary ( 2 carbons) and Tertiary ( 3 carbons) Carbolic Acids Compounds that have the carboxyl, -COOH functional group The ending -oic acid denotes that we are dealing with a carboxylic acid. • Are relatively weak acids. Esters These are compounds that have the C-O- C functional group. Esters arise by the reaction between a carboxylic acid and an alcohol: All esters consist of two parts in their name: oFirst part: an alkyl derived from the alcohol used, oSecond part (separate word) ends in -anoate derived from a carboxylic acid (has the double bond O) Ketones Functional group: Carbonyl group (C=O) found in the middle of the molecule Suffix: -one ( pronounced own) Example: propanone The carbonyl group (C=O) is polar. Aldehydes Functional group: Carbonyl group (C=O) found at the end of the molecule Suffix: -al Example: propanal ISOMERS Isomers are compounds which have the same molecular formula, but different structural formulae. OH
Physical Sciences P2 Learner’s Guide Exam School 2012 Mindset Learn Xtra Exam School is brought to you by Page 21 PHYSICAL PROPERTIES OF ORGANIC MOLECULES Molecules are held together by intermolecular forces. In order to separate these molecules from each other requires energy. The stronger the intermolecular forces, the more energy that is required to separate or break these bonds. This will lead to a higher melting point, boiling point, etc. Boiling and Melting Points As the strength of the intermolecular forces increase, the boiling point and melting point will increase. Thus molecules where there are hydrogen bonds present will have a higher melting point and boiling point than those molecules where there are weaker London forces or Van der Waals forces present. Vapour Pressure Vapour pressure is the amount of pressure that the gaseous molecules exert above the surface of the liquid phase. The vapour pressure will decrease as the size of the molecule increases (chain length). Vapour pressure is an indication that there are weak intermolecular forces present in the liquid phase. Viscosity A liquid that has a low viscosity will be able to flow more easily. Thus, where hydrogen bonds are present, there will be a much higher degree of viscosity. The opposite is true for the weak Van der Waals forces. Viscosity will also increase as the length of the carbon chain increases. Density The density of organic molecules will increase as the length of the chain increases. Surface Area As the surface area of the molecule decreases, there will be lower boiling and melting points as the intermolecular forces will be weaker. Phases As the chain length increases, the melting and boiling points will increase. The smaller molecules will then be gases at room temperature and the longer chain lengths will be liquids or solids at room temperature
Physical Sciences P2 Learner’s Guide Exam School 2012 Mindset Learn Xtra Exam School is brought to you by Page 22

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