CEM 251 Midterm 1 Study Guide
CEM 251 Midterm 1 Study Guide CEM 251
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This 11 page Study Guide was uploaded by Sarah Struble on Friday September 25, 2015. The Study Guide belongs to CEM 251 at Michigan State University taught by C. Vasileiou in Fall 2015. Since its upload, it has received 498 views. For similar materials see Organic Chemistry I in Chemistry at Michigan State University.
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Date Created: 09/25/15
1 of 11 CEM 251 Midterm 1 Study Guide Valence Electrons electrons in outermost shell ex Carbon above has 4 electrons in the secondoutermost shell Formal Charge of valence electrons of electrons in lone pairs of shared electrons N02 FC5O41 2 e formal charge of 1 1 e radical no charge Valence is also the of electrons an atom needs to gain nonmetals or lose metals to get to the full octet Octet Rule most atoms would like to have electron configuration of a noble gas with 8 valence electrons Atom Valence gt of bonds to be neutral I C 4 H 1 O 2 N 3 Halogens 1 Carbon 4 bonds to be neutral NEVER MORE can be less 3 bonds I I I c C Q 3 bonds no 0nc pair 3 bomb v lone pair 3 bonds unpaired electron carboeation earhanion carbon radical Oxygen 2 bonds to be neutral lone pairs can be used to make third bond 3 bonds O 0 90 Oxygen formal charge quot 339 I 6 valence e 2 lone e 3 e in bonds1 positive formal charge 3 bonds l lone pair 1 bond negative formal charge 1 bond 3 lone pairs 2 of 11 Nitrogen 3 bonds to be neutral use lone pair to make 4th 4 bonds N m 4quot N m Nitrogen formal charge z quot l 5 valence e 0 lone e 4 e in bonds 1 ms mn39 mm 134439 39 J Hutch 2 bonds uncommon Halogens F Cl Br I 1 bond to be neutral Cl H lone pairs can make 2nd bond but it is less common than N or O Electron Configuration o Rule 1 Aufbou Building up lower to higher 1s gt2s2 gt2p6 gt3s2 gt3p6 gt4s2 First shell one sorbital 2 electrons Second shell two sorbitals and 3 porbitals with 2 electrons in each 8 electrons Rule 2 Only 2 e per orbital Rule 3 Hund s Rule put one e in each orbital before pairing A I l I 2p 1 25 I and s Rule J Hcmmm mmp wparatr ls quotHuh rather than pair Atoms gt Molecules Molecular Orbitals Types of Bonds Single bonds sigma bonds 0 bond many ways to form singlesigma bonds Doubletriple bonds pi bonds rtbonds double bonds have one sigma bond and one pi bond triple bonds have one sigma bond and 2 pi bonds pi bonds are ONLY formed by combination of two p orbitals 30f11 Single Bonds T 109 5 H Tetrahedral gt r H C H 4 equivalent bonds i I 4 equivalent orbitals H I l H Why are the bonds identical hybridization combining orbitals Ener A gy all 4 valence electrons need to be mixed 2p 9 9 n sp3 orbital makes it so that they are 9 9 9 9 SpJ all equal energy if an atom ONLY has single bonds it quot 39 is sp3 25 i w ALL sp3 Carbons H sigmabond H made from combining s orbital from H Sigmabond and sp3 orbital SP3 Sp3 from C any C H bond s sp3 since H only has ts orbital any C C bond sp3 sp3 generalize O N with only single bonds sp3 Double Bonds planar molecules always one sigma bond one pi bond H H pi bond pp sigma bond H spzsp2gt hybridization of 2s and 2p orbitals 1 2p 1 1 1 2p 1 25 gt I I I sp hybrid in 4H any atom with double bonds sp2 Triple Bonds one sigma bond 2 pi bonds planarAND linear molecules A 2p 1 2p u 39b id r39 n 39 I r uh I I Sp 2 1 Be Be excited state sp hybridized 39 39 pi bonds pp H ngma bond SpSp any atom with triple bonds sp Practice C b0nd sp3 sp3 SP o bond atom SW SW o bond 1 o bond Sp Sp 2 pibonds Io p 40f l l 50f11 Resonance Structures Resonance movement of electrons in molecules rearranging electrons Rules do not makebreak sigma bonds conserve charge only electrons in pibonds lone pairs and charges Ex N02 7 CG 0 I n 1 Broke double bond gt NU NVquot 2 Formed new double bond is v overall neutral EX Cquot 3 39 i 1quot Charged molecules keep their 39u lt H original charge l Most stable because the charge is on the most electronegative atom EX Valid structure but NOT STABLE because too many charges ltgt ltrgt 39 N LN gt Ex Resonance Structures with Lone Pairs 21 ICEJ ktA quot lt4 AQZA l Most stable structure 6 of 11 AcidBase Chemistry Lewis Acid e acceptor Lewis Base e donator Bronsted Acid H donator Bronsted Base H acceptor a gr H iJ I 5quot l M l Acid Base Water Salt k A f r v E H l ql 139 H V 39 M r k U Acid Base f39 Salt Acid Base reactions happen when the electrons from a charged or partially charged atom ATTACK a hydrogen atom in a separate molecule It takes the H ion and forms a bond with it and the hydrogen s oriiinal bond breaks a A Q 3 H A 4 hlk H 39 Add Base Conjugate Conjugate Base ACid pKa number that tells how acidic something is always comparativerelative lowER pKa stronger acid weaker base highER pKa weaker acid stronger base Some pKa s to remember Inorganic Acid not connected to any carbons H Cl pKa 7 VERY LOW Carboxylic Acid pKa 5 0 RCOH 7 of 11 Water H O H pKa 16 Alcohol pKa16 OH Ammonia NH3 likes to share it s electrons more pKa35 more basic Use pKa to figure out the direction of equilibrium Acid Base reactions go from stronger acid to weaker acid The direction of equilibrium is to the left from stronger acid to weaker acid 4 m 4 C 1 I quotA TCCH c r 1 A F H v H rl I ConjugateAcid Add20399 1 H produced when base P 3 gains H pKa 5 Weaker Acid Stronger Acid Stronger Acids Have MOST stable conjugate base HCI is a stronger acid than water H Cl H Cl H O H H OH Cl holds a negative charge better than OH so it is more stable Have a conjugate base with more STABLE resonance structures Carboxylic Acid f 39 pKa5 A v Charge can also be L spread out between lt 3 Y I the 2 highly 3 electronegative 39Q oxygens J Another way to hold the charge resonance structure 8of11 Alcohol O H H pKa1 6 No other way to hold the charge No resonance structures Alcohol and water have the same pKa because both of their conjugate bases do not have resonance structures Phenol H A V pKa1 0 gtlt Q 3 3 resonance structures so phenol is more acidic than alcohol BUT it is LESS acidic than carboxylic acid because it does not have 2 oxygens on it to spread the charge out An acid is stronger if its conjugate base is MORE STABLE What makes a conjugate base stable it has more resonance structures Note if one of the resonance structures is an opposing structure ie it has two like charges next to each other then it DOES NOT COUNT and does not make the conjugate base more stable It has two or more electronegative atoms in it to delocalize the charge The closer the electronegative atom is to the charge the more stable the conjugate base therefor the stronger the acid 90f11 Naming Molecules IUPAC I Prefix prefix parent name suffix if it is in a ring add cyclo before prefix 1 meth if only single bonds suffix ane 2 eth prefix the number of carbons in the longest chain Steps 3 prop 1 Find the longest continuous carbon chain and count the carbons 4 but never combine ring structure and side group to make a continuous chain if there are only single bonds add ane after the appropriate prefix 5 pent 2 If there is a side group coming off of the carbon chain number the 6 hex carbon chain in a way that will make the side group coming off of the lowest possible carbon number 7 hept 3 Carbon based side groups have suffix yl and its prefix is the number 8 oct of carbons In It on chart gt 4 Put the number carbon that the side group comes off of before the side 9 non group name with a dash ex 3methyl if there is a methyl group coming off of the 3rd carbon in the continuous carbon chain that you numbered 10 deC in step 1 5 If there are two side groups for the final name put them in alphabetical order ex 3ethyl 1methyl pentane if they have the same number of carbons ie two methyl groups add the prefix di and then put the number carbon they each appear on separated by a comma ex 13dimethyl the d in di does not count when putting groups in alphabetical order 6 If the side group is NOT carbon based it will end in o and start with the element s common name ex Cl on the 3rd carbon in the continuous chain would be called 3chloro 2 6carbon chain 1 Q numbered 30 that the l H t 1carbon hexane methyl group is on the Side group 39 S 9 lowest possible number quot 3 methyl 7 L I I t 39bl H3 i quot onges pOSSI e 1Carbon Side longest pOSSIble contlnuous carbon rou meth I continuous carbon 4 chain 9 p y Chain 5 4 8carbon ring 339methyl hexane 1methyl cyclooctane z 3f longest chain l I 5ethyl3methyl octane 25dimethyl heptane alphabetical order Chlorine side group chloro coming off of first carbon Nitrogen side 10 0f 11 group nitro 2carbon side group ethyl gt longest chain 1chloro ethyl 5 coming off 6th carbon 61chloro ethyl 3nitro nonane Newmann Projection different way of looking at molecules and bonds molecules can rotate around their bonds ex CH3CH3 if you rotate this structure around the 0 0 bond it s structure will change l T C quot I H gt going into page H l L H H gtcoming out of page Newmann structure looking at this molecule from the side 1 Elipsed structure when both sides are aligned least stable Rotate the back part 60 degrees H H H Staggered structure the two sides are staggered far apart most stable I H H 11 Of 11 Least stable Newmann Structure the two biggest parts of the molecule H IH 600 are right next to each other p gt aka Gauche conformation H CH3 H CH3 MOST stable Newmann Structure the two biggest parts of the molecule are as far apart as possible aka Anticonformation CH3 Another example I eyes Most stable U u H H
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