Classes of Organic Compounds

Transcription

1 Unit 1 Functional Groups Depicting Structures of rganic ompounds Lewis Structures ondensed structural formulas Line angle drawings 3-dimensional structures Resonance Structures Acid-Base Reactions urved Arrows

2 lasses of rganic ompounds rganic compounds are commonly classified and named based on the type of functional group present. An atom or group of atoms that influences the way the molecule functions and reacts. The center of reactivity in an organic compound

3 lasses of rganic ompounds You must be able to recognize and draw the functional groups listed in your syllabus and on the following slides. Use the following slides and the tables given in the front of your text and in the chapter to learn these.

4 Functional Groups lass of ompound Functional Group Alkane ycloalkane Alkyl halide Alkene Alkyne Alcohol Ether None None X

5 Functional Groups lass of ompound Aldehyde Ketone arboxylic Acid Acid hloride Ester Functional Group l

6 Functional Groups lass of ompound Functional Group Amine N R R' Amide N R R' Nitrile N Aromatic ring

7 Alkanes ontain - single bonds no functional group Nonpolar covalent bonds electrons shared equally Tetrahedral electron domain geometry sp 3 hybridized carbons

8 ycloalkanes ontain with at least 3 of the carbons arranged in a cyclic (ring) structure No functional group Nonpolar Tetrahedral sp 3 hybrid orbitals c c c c c

9 Alkenes ontain = (carbon-carbon double bonds) 1 sigma bond & 1 pi bond Non-polar Trigonal planar geometry 3 2 = Which atoms must be coplanar in an alkene? sp 2 hybridized carbons 2 = 3

10 Alkenes The = present in an alkene is composed of 1 sigma (s) bond and 1 pi (p) bond. A sigma (s) bond forms when two orbitals overlap end to end. electron density is centered along the internuclear axis cylindrically symmetrical Internuclear axis

11 Alkenes A pi (p) bond forms when two p orbitals overlap side to side electron density is located above and below the internuclear axis oriented parallel to the internuclear axis

12 Alkenes Free rotation occurs around single bonds. Double and triple bonds are rigid. annot rotate freely. Rotation would cause loss of overlap of the p orbitals, destroying the p bond.

13 Alkynes ontain triple 3 bonds 1 sigma bond 2 pi bonds Nonpolar 2 = 3 Linear electron domain geometry 2 = 3 sp hybridized carbons 3 Which atoms must be co-linear in an alkyne?

14 Aromatic Ring Planar ring system with alternating single and double bonds does not react like an alkene 3 3 Nonpolar Trigonal planar sp 2 Ph hybridized carbons Benzene ring is a very common aromatic ring. Ph 3 3 Ph 3 3 Ph 3 3 Ph N.. N

15 ontain -halogen bond F, l, Br, or I Alkyl alides Polar covalent -halogen bond 2 = 3 electrons shared unequally - Br = 3 Many (but 3 (Br) not 2 all) 3 alkyl halides are polar Br molecules as well. Br (Br) 2 3 Br 2 = 3 2 = 3 2 = 3 Br Br Br 3 (Br) (Br) 2 3 Br Br 3 (Br) - Br -

16 Polar ovalent Bonds Two ways to indicate bond polarity partial charges - on more electronegative element + on less electronegative element direction of dipole moment + on less electronegative element arrow pointing toward more electronegative element

17 Polar ovalent Bonds Dipole moment: A measure of the separation and magnitude of the positive and negative charges in polar bonds or polar molecules. Important Polar ovalent Bonds: - -N -halogen - N- -halogen Important Nonpolar ovalent Bonds: - - halogen-halogen

18 Polar Molecule: Polar Molecules a molecule with a non-zero molecular dipole moment net negative end, net positive end contains 1 or more polar covalent bonds arranged asymmetrically within the molecule use molecular geometry to determine polarity exhibit dipole-dipole interactions ow does the BP of a polar molecule compare to the BP of a nonpolar molecule with similar molar mass? - + +

19 Nonpolar Molecules Nonpolar molecules: a zero (or very small) molecular dipole moment contain either: only nonpolar covalent bonds 2 or more polar covalent bonds arranged symmetrically London dispersion forces found in all molecules only IMF found in nonpolar molecules strength increases as surface area increases What variables make SA increase? What happens to the BP as SA?

20 Polar/Nonpolar Molecules Example: Which of the following are polar molecules? Br l 4 l l Br Br Br Br

21 Alcohols 3 () 2 ( 3 ) 2 3 () 2 ( ontain -- bond hydroxyl group Polar covalent bonds - bond - bond Polar molecule dipole-dipole interactions hydrogen bonding What causes hydrogen bonding? ow does hydrogen bonding affect BP? 3 () 2 ( 3 ) 2

22 Ethers ontain -- bond Polar covalent bonds tetrahedral e.d. geometry bent molecular geo. 3 3 () 2 ( 3 ) 2 3 () 2 ( 3 ) 2 Polar molecules dipole-dipole interactions 3 () 2 ( 3 ) ( 3 2 ) ( 3 2 ) 2 ( 3 2 ) 2

23 Amines N ontain -N-R R Polar covalent 3 bonds N 3 Polar molecules Dipole-dipole interactions ydrogen bonding N (1 o and 2 o ) ommon organic bases lone pair of e - on N 3 N 2 3 N 3 ( 3 ) 3 N 1 o 2 o 3 o primary secondary tertiary N N N 2 N 3 3 N N N

24 Aldehydes ontain - (-) arbonyl (=) always on the 1st or last carbon in a chain trigonal planar geometry sp 2 hybrid orbitals Polar covalent bond Polar molecule dipole-dipole interactions

25 Ketones ontain -- arbonyl attached to middle of chain Polar covalent bond Polar molecule 3 () 3 dipole-dipole interactions Trigonal planar e.d. geo. sp 2 hybridized 3 3 () 3 () 3 3 ()

26 N N arboxylic Acids 3 N 2 3 N 2 3 N 3 N 3 ( 3 3 )( 3 N 3 ) 3 N 1 o 1 o 2 o 2 o 3 o 3 o ontain carboxyl group Polar covalent bonds Polar molecules dipole-dipole hydrogen bonding trigonal planar sp 2 hybridized carbon

27 Acid hloride ontain Polar molecule dipole-dipole forces l l Trigonal planar geo. sp 2 hybridized l Lachrymators l

28 ontain Esters - 2 R where R = alkyl group Polar covalent bonds Polar molecules dipole-dipole interactions trigonal planar sp 2 hybridized R where R = alkyl group

29 ontain Amides N where R and R = or alkyl Polar covalent bonds Polar molecules dipole-dipole interactions hydrogen bonding (1 o and 2 o ) N 3 2 N 2 3 N N 3 2 N 2 3 = is trigonal planar & sp 2 hyrbridized N N 2 3 N 3 3 N( 3 ) 2-2 R where R = alkyl group 1 o 2 o 3 o - 2 R where R = alkyl group N

30 Nitriles 3 N 2 3 N 1 o N 2 3 ontain N N Polar covalent bond Polar molecule dipole-dipole 3 N Linear, sp hybridized 3 N 2 3 N 3 3 N( 3 ) 2 o o o

31 Functional Groups 2 Example: Identify the functional N groups N present in the following compounds. N 2 N N N testosterone Vanillin Lisinopril

32 Depicting Structures of rganic ompounds rganic compounds can be described using a variety of formulas: Empirical formula Molecular formula Lewis structure Full structural formula Three dimensional drawings ondensed structural formula Line angle drawings

33 Depicting Structures of rganic ompounds Ethyl acetate is an organic molecule with: empirical formula = 2 4 lowest whole number ratio molecular formula = actual number of each type of atom present

34 Depicting Structures of rganic ompounds Ethyl acetate is an organic molecule with: Lewis structure: depicts all covalent bonds using a straight line and shows all nonbonding pairs of electrons What are covalent bonds? Full structural formula: a Lewis structure without the nonbonding electrons

35 Depicting Structures of rganic ompounds Ethyl acetate is an organic... molecule with: 3-D drawing: ondensed structural formula Line angle drawing

36 Lewis Structures Lewis structures are used to represent the covalent bonds present in a molecule. Symbol for each atom ovalent bonds between atoms depicted using a solid line Unshared electrons are shown around the appropriate atom

37 Lewis Structures To draw a Lewis structure: ount the number of valence electrons For a cation (+), subtract 1 electron for each positive charge N 4 + : (1) -1 = 8 e - For an anion (-), add 1 electron for each negative charge N - : = 10 e -

38 Lewis Structures Draw a skeleton structure showing the chemical symbol for each atom. onnect the appropriate atoms using a single bond. Skeletons for organic compounds: The backbone generally contains - bonds N,, and S can either be part of the backbone or attached to one of the carbons as a substituent. will be attached to,n,s and/or alogens will be attached to as substituents.

39 Lewis Structures Add pairs of electrons to the atoms giving each one an octet only gets 2 electrons Try filling the octets of N,, S, and halogens first There will generally NT be any leftover electrons for organic compounds. rganic ions, however, may have leftover electrons. Put them on an atom that needs an octet.

40 Lewis Structures If there are not enough electrons to give all atoms an octet, share electrons to form multiple bonds. Single bond: one pair of electrons shared l double bond: two pairs of electrons shared triple bond: three pairs of electrons shared N N

41 Lewis Structures ommon 3 2 neutral bonding patterns N N. N N... N.... Br... Br... Br... Br..... B. N alogens total bonds lone pairs

42 Lewis Structures Example: Draw the Lewis structure for 2 3 I.

43 Lewis Structures Example: Draw the Lewis structure for a ketone with the molecular formula, 5 9 Br.

44 Lewis Structures Example: Draw two possible Lewis structures for These two Lewis structures are resonance structures.

45 Formal harge Which atom in each of the previous Lewis structures is negatively charged? Formal charge provides a method for keeping track of electrons in a compound. determines which atom(s) in a structure bear(s) the charge in a polyatomic ion identifies charged atoms within a molecule that is neutral overall.

46 Formal harge Formal charge: - a calculated value that compares the number of valence electrons.. for.. a... particular atom to the number of electrons assigned to that atom in a Lewis structure. F = group # - nonbonding e /2 (bonding e - ) F = /2(2) -1

47 Formal harge ommon rganic Bonding Patterns and Formal harges: Positive Neutral Negative + - N N + N N - + -

48 Formal harge Example: alculate or determine the formal charge on N and in ( 3 ) 3 N. All Lewis structures you draw from now on should include any non-zero formal charges that are present.