3-MED101_Alkanes_Alkenes_Alkynes.pptx

MED100 MOLECULAR AND CELLULAR MEDICAL SCIENCES I Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected]  Lecture Presentation...

MED100 MOLECULAR AND CELLULAR MEDICAL SCIENCES I Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected]  Lecture Presentation Alkanes, Alkenes, Alkynes Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED101 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  Introduction to Alkanes and Cycloalkanes Hydrocarbons in which all of the carbon–carbon bonds are single bonds are called alkanes, those hydrocarbons that contain a carbon–carbon double bond are called alkenes, and those with a carbon– carbon triple bond are called alkynes. Cycloalkanes are alkanes in which all or some of the carbon atoms are arranged in a ring. Alkanes have the general formula CnH2n+2; cycloalkanes containing a single ring have two fewer hydrogen atoms and thus have the general formula CnH2n. Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I In this Chapter; You will learn Introduction to Alkanes and Cycloalkanes Shapes of Alkanes How To NAME Alkanes How To Name Unbranched Alkyl Groups How To Name Branched-Chain Alkanes How To Name Branched Alkyl Groups How To NAME cycloalkanes How To Name Alkenes and Cycloalkenes How To Name Alkynes  Shapes of Alkanes Unbranced Alkanes Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  Shapes of Alkanes Branched Alkanes Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To NAME Alkanes Today, chemists use a systematic nomenclature developed and updated by the International Union of Pure and Applied Chemistry (IUPAC). The ending for all of the names of alkanes is -ane. Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Unbranched Alkyl Groups If we remove one hydrogen atom from an alkane, we obtain what is called an alkyl group. These alkyl groups have names that end in -yl. When the alkane is unbranched, and the hydrogen atom that is removed is a terminal hydrogen atom, the names are straightforward: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes 1. Locate the longest continuous chain of carbon atoms; this chain determines the parent name for the alkane. We designate the following compound, for example, as a hexane because the longest continuous chain contains six carbon atoms: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes 2. Number the longest chain beginning with the end of the chain nearer the substituent. Applying this rule, we number the two alkanes that we illustrated previously in the following way: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes 3. Use the numbers obtained by application of rule 2 to designate the location of the substituent group. The parent name is placed last, and the substituent group, preceded by the number designating its location on the chain, is placed first. Numbers are separated from words by a hyphen. Our two examples are; 2-methylhexane and 3-methylheptane, respectively: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes 4. When two or more substituents are present, give each substituent a number corresponding to its location on the longest chain. For example, we designate the following compound as 4-ethyl-2-methylhexane: The substituent groups should be listed alphabetically (i.e., ethyl before methyl).* In deciding on alphabetical order, disregard multiplying prefixes such as “di” and “tri.” Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes 5. When two substituents are present on the same carbon atom, use that number twice: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes 7. When two chains of equal length compete for selection as the parent chain, choose the chain with the greater number of substituents: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched-Chain Alkanes 8. When branching first occurs at an equal distance from either end of the longest chain, choose the name that gives the lower number at the first point of difference: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  Exercise: Provide an IUPAC name for the following alkane Answer: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  Exercise: Which structure does not represent 2-methylpentane? Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched Alkyl Groups For alkanes with more than two carbon atoms, more than one derived group is possible. Two groups can be derived from propane, for example; the propyl group is derived by removal of a terminal hydrogen, and the 1-methylethyl or isopropyl group is derived by removal of a hydrogen from the central carbon: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched Alkyl Groups Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Branched Alkyl Groups Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To NAME cycloalkanes How To Name Monocyclic Cycloalkanes Cycloalkanes are named by adding “cyclo” before the parent name. 1. Cycloalkanes with one ring and no substituents: Count the number of carbon atoms in the ring, then add “cyclo” to the beginning of the name of the alkane with that number of carbons. For example, cyclopropane has three carbons and cyclopentane has five carbons. Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To NAME cycloalkanes 2. Cycloalkanes with one ring and one substituent: Add the name of the substituent to the beginning of the parent name. For example, cyclohexane with an attached isopropyl group is isopropylcyclohexane. For compounds with only one substituent, it is not necessary to specify a number (locant) for the carbon bearing the substituent. Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To NAME cycloalkanes 3. Cycloalkanes with one ring and two or more substituents: For a ring with two substituents, begin by numbering the carbons in the ring, starting at the carbon with the substituent that is first in the alphabet and number in the direction that gives the next substituent the lower number possible. When there are three or more substituents, begin at the substituent that leads to the lowest set of numbers (locants). The substituents are listed in alphabetical order, not according to the number of their carbon atom. Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To NAME cycloalkanes 4. When a single ring system is attached to a single chain with a greater number of carbon atoms, or when more than one ring system is attached to a single chain, then it is appropriate to name the compounds as cycloalkylalkanes. For example, Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkenes and Cycloalkenes The IUPAC rules for naming alkenes are similar in many respects to those for naming alkanes: 1. Determine the parent name by selecting the longest chain that contains the double bond and change the ending of the name of the alkane of identical length from –ane to -ene. Thus, if the longest chain contains five carbon atoms, the parent name for the alkene is pentene; if it contains six carbon atoms, the parent name is hexene, and so on. Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkenes and Cycloalkenes 2. Number the chain so as to include both carbon atoms of the double bond and begin numbering at the end of the chain nearer the double bond. Designate the location of the double bond by using the number of the first atom of the double bond as a prefix. The locant for the alkene suffix may precede the parent name or be placed immediately before the suffix. We will show examples of both styles: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkenes and Cycloalkenes 3. Indicate the locations of the substituent groups by the numbers of the carbon atoms to which they are attached: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkenes and Cycloalkenes 4. Number substituted cycloalkenes in the way that gives the carbon atoms of the double bond the 1 and 2 positions and that also gives the substituent groups the lower numbers at the first point of difference. With substituted cycloalkenes it is not necessary to specify the position of the double bond since it will always begin with C1 and C2. The two examples shown here illustrate the application of these rules: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkenes and Cycloalkenes 5. Name compounds containing a double bond and an alcohol group as alkenols (or cycloalkenols) and give the alcohol carbon the lower number: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkenes and Cycloalkenes 6. Two frequently encountered alkenyl groups are the vinyl group and the allyl group: Using substitutive nomenclature, the vinyl and allyl groups are called ethenyl and prop-2-en-1-yl, respectively. The following examples illustrate how these names are employed: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  Exercise: Give an IUPAC name for the molecule shown Answer: We number the ring as shown below starting with the hydroxyl group so as to give the double bond the lower possible number. We include in the name the substituent (an ethenyl group) and the double bond (-ene-), and the hydroxyl group (- ol) with numbers for their respective positions. Hence the IUPAC name is 3- ethenyl-2-cyclopenten-1-ol. Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkenes and Cycloalkenes 7. If two identical or substantial groups are on the same side of the double bond, the compound can be designated cis; if they are on opposite sides it can be designated trans: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  Exercise: Give IUPAC names for the following alkenes: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  Exercise: Write bond-line formulas for the following: (a) cis-3-Octene (b) trans-2-Hexene (c) 2,4-Dimethyl-2-pentene (d) trans-1-Chlorobut-2-ene (e) 4,5-Dibromo-1-pentene (f) 1-Bromo-2-methyl-1-(prop-2-en-1-yl)cyclopentane (g) 3,4-Dimethylcyclopentene (h) Vinylcyclopentane (i) 1,2-Dichlorocyclohexene (j) trans-1,4-Dichloro-2-pentene Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkynes Alkynes are named in much the same way as alkenes. Unbranched alkynes, for example, are named by replacing the -ane of the name of the corresponding alkane with the ending -yne. The chain is numbered to give the carbon atoms of the triple bond the lower possible numbers. The lower number of the two carbon atoms of the triple bond is used to designate the location of the triple bond. When double and triple bonds are present, the direction of numbering is chosen so as to give the lowest overall set of locants. In the face of equivalent options, then preference is given to assigning lowest numbers to the double bonds. The IUPAC names of three unbranched alkynes are shown here: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I  How To Name Alkynes The locations of substituent groups of branched alkynes and substituted alkynes are also indicated with numbers. An −OH group has priority over the triple bond when numbering the chain of an alkynol: Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I Altınbas University Lecturer: Asst. Prof. Behiye ÖZTÜRK ŞEN [email protected] MED100 MOLECULLAR AND CELLULAR MEDICAL SCIENCES I