Chem 219: Module 2 Exam Questions With 100% Correct Answers

Chem 219: Module 2 Exam Questions With 100% Correct Answers What are hydrocarbons? - answerMolecules composed of only the elements carbon and hydrogen What are the two major classes of hydrocarbons? - answerAromatic (benzene) and aliphatic (alkanes, alkenes, alkynes) What is the main source of hydrocarbons? - answerFossil fuels like coal, petroleum, and natural gas obtained by mining and drilling. What are Alkanes? - answerThey are saturated hydrocarbons because their skeleton is only composed of C-C single bonds. How can alkanes exist? - answerThey can be linear, branched or exist in ring formations called cycloalkanes. Describe a higher/more complex alkane structure: - answerThey will have more carbons and/or increased structural diversity. What is the general formula of Alkanes? - answerCnH2n+2 The names of the alkanes reflect? - answerThe number of carbons present. How many isomers does each alkane have from 1-10 - answer1,1,1,2,3,5,9,18,35,75 Name the first ten prefix of alkanes: - answerMethane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane. As the molecular weight increases: - answerThe number of isomers increase. What does the suffix -ane mean? - answerDenotes a saturated hydrocarbon. It is used for all acyclic saturated alkanes What is nomenclature? - answerThe naming of a molecular structure. Historically they were named after their source, now they are systemic. Why is nomenclature important? - answerBecause we cannot remember all the prefixes since a MF composed of carbons can have several different patterns of connectivity. What is it meant by the systemic approach? - answerThere are now methods of naming molecules so that they all have unique names. You can then determine the structure from only the name and vice-versa. IUPAC rules for naming branced alkanes: - answer1. Find the parent name by identifying the longest continuous chain of carbons. 2. Number the parent chain. (begin at the end of the chain nearest to the first branch.) 3. If there are two equally long continuous chains, select the one with most branches. 4. If the first branch point is the same distance, choose the one that gives the lowest substituents. 5. If the substituents are both equidistant then choose the numbering so the substituent goes with the higher alphabetic priority. How are linear alkanes named? - answerBy combining the prefix indicating the number to the suffix -ane. What is a substituent? - answerAny group attached to the parent chain. What are alkyl groups? - answerSaturated hydrocarbon substituents. You drop the -yl for - ane. A one carbon substituent is a methyl group, four carbon is butyl. What is a locant? - answerA number used to determine the suffix. Describes the position of substituents. What happens when two or more of the same type of substituents are present on the parent chain? Like 3 methyl groups - answerAdditional prefixes including the number are added. How would you describe finding 2,3 dimethylpentane? - answerIt is a 5 carbon chain, then it has substituents on numbers 2, 3 and those are methyl groups. How are IUPAC systematic names put together? - answerLocant-(prefix) substituentparent If two or more different substituents are present on the parent chain then what happens? - answerThey are listed alphabetically. Ethyl before methyl How are halogen atoms as substituents named? - answerChange the -ine to -o, chlorine=chloro, bromine=bromo. propyl or n-propyl - answerCH3CH2CH2 isopropyl - answerCH3CHCH3 What does the squiggle bond mean? - answerPoint of attachment to the parent chain.