Jalaram Choudhary fb.com/neetbooklet
9
CHEMISTRY
Energy Energ y of electron in species with one electron. -2p 2 me4 Z2 En = n 2h 2 For energy in SI system, -2p2 me4 Z2 En = 2 2 n h (4pe0 ) 2
ATOMIC STRUCTURE
2
En =
-1312Z n
2
(a) % ioni ionicc chara charact cter er = CHEMICAL BONDING
1 é - (XA - X B ) ù ê úû = 100 ë1 - exp 4
kJ mol-1
Fajan’s Factors : Following Following factors are helpful in bringing
where e0 is permitivity constant and its value is 8.8542 × 10 –12 coulomb2 newton –1 metre –2
covalent character in Ionic compounds (a) Small cation (b) Big anion (c) High charge on cation/anion (d) Cation having pseudo p seudo inert gas configuration (ns2 p6d10) e.g. Cu+, Ag+, Zn Zn+2, Cd+2 M.O. theory : (a) Bond ord order er = ½(N ½(N b –Na) (b) Higher Higher the bond bond order, order, higher higher is the bond bond dissoc dissociatio iationn energy, energy, greater is i s the stability, stability, shorter is the bond length. S p e c i e s B o n d order Magnetic properties (c) H2 1 Diamagnetic + H2 00..5 Paramagnetic Li2 1 Diamagnetic 3 2 2 Relative bond strength : sp d >dsp >sp3 >sp2 >sp >p-p (Co-axial) > s - p > s - s > p - p (Co-lateral) VSEPR theory (a) (LP-LP) repulsion r epulsion > (LP-BP) > (BP-BP) (b) NH3 ® Bond Angle 106° 45’ because (LP-BP) repulsion > (BP-BP) H2O ® 104° 27’because (LP-LP) repulsion > (LPLB) > (BP-BP) Bond angle : (a) NH3 > PH3 > AsH3 (b) H2O > H2S > H2Se (c) NH3 > NF3 (d) Cl2O > OF2
æ n2 ö n 2h 2 r= 2 = 0.529 çç ÷÷ Å 4p mZe 2 èZø Total Total energy of electron in the nth shell e2 æ kZe 2 ö kZe 2 + == K.E. + P.E. = kZ 2r çè rn ÷ø 2rn
u=
1
l
é1 1ù - 2 ú , [R = 1.0968 × 107 m –1] 2 n ëê 1 n 2 ûú
= RZ RZ2 ê
No. of spectral lines produced when an electron drops from n (n - 1) nth level to ground level = 2 Heisenberg Uncertainty Principle (Dx) (D p) ³ h/4p Nodes (n – 1) = total total nodes, l = angular nodes, (n – l – 1) = Radial n odes Orbital angular momentum :
l (l + 1)
Radial probability density curves: n=1
r d . 2 r
l( l + 1) h
n=2
2
1s
p
4 . R
r d . r p 4 .
h = 2p
2
2s
Δn
2
R
r
®
®
r
CHEMICAL r d . 2 r
n =2
n=3 3s
p
4 . 2 R
r d . r p 4 .
r d . 2 r p 4 .
EQUILIBRIUM 2p
2
®
R
r
n=3
2
r d . r p 4 .
2
3p
2
Actual dipole moment ´100 Calculated dipole moment (b) Pa ul i ng eq ua ti on % ionic character
r
®
n=3 3d
K p = K c (RT) g where Dng' nP – nR Free Energy change (DG) (a) If DG = 0 then reversible reversi ble reaction would be in equilibrium, K c = 0
(b) If DG = (+) ve then equilibrium will be displace displace in backw backward ard direction; direction; K c < 1 (c) If DG = (–) ve then equilibriu equilibrium m will displace in forward direction; K c > 1 (a) K c unit ® (moles/lit)Dn, (b) K p unit ® (atm)Dn
2
R ®
r
R ®
r
"CheMentor"
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10 Reaction Quotient and Equilibrium Constant
Consider the following following reversible r eversible reaction A+BC+D [C][D]
\ Qc = [A][B] Case I : If Q c < K c then : [Reactants] > [Products]
then the system is not at equilibrium Case II : If Qc = K c then : The system is at equilibrium and the concentration concentration of the species species C, D, B,A are at equilibrium. Case III : If Q c > K c then : [Products] > [Reactants] The system is not at equilibrium. A relationship between the equilibrium constant K C, reaction quotient and an d Gibbs energy. DG = DG° + RT ln Q At equilibrium DG = 0 and Q = K then DG° = –RT – RT ln K c \ DG° = –RT ln K p Le chatelier’s principal (i) Increase Increase of of react reactant ant conc. conc. (Shif (Shiftt forwa forward) rd) (ii) ii) Decrease Decrease of reactant conc. conc. (Shift backward) backward) (iii (iii)) Increase of pressure (from more moles to less moles) moles) (iv) (iv) Decrease Decrease of pressure pressure (from less less moles to more moles) moles) (v) (v) For exothermic reaction decrease in temp. temp. (Shift (Shift forward) (vi) (vi) For endothermic endothermic increase increase in temp. (Shift backward) backward) (a) Lewi Lewiss Acid Acid (e – pair acceptor) ® CO2, BF3, AlCl3, ZnCl2, normal cation (b) (b) Lew Lewis Bas Basee (e – pair donor) NH3, ACIDS AND ROH, ROR, H2O, RNH2, normal BASES anion Dissociation of weak Acid & Weak Base ® (a) Weak Ac Acid ® K a = Cx2/(1 – x) or K a = Cx Cx2 ; x << 1 2 (b) (b) Weak eak Bas Basee ® K b = Cx /(1 – x) or K b = Cx2 ; x << 1 Buffer solution {Henderson equation} : (a) Acidic ® pH = pK a + log {Salt/Acid}. {Salt/Acid}. For Maximum buffer action pH = pK a Range of Buffer pH = pK a ± 1 (b) Alkali aline ® pOH = pK b + log {Salt/Base} for max. buffer action pH = 14 – pK b Range pH = 14 – pK b ± 1 Moles/ oles/ lit of Aci Acid or Bas Base Mixe ixed (c) (c) Buff Buffer er Capaci Capacity ty = chan change ge in pH Necessary Necessary condition condition for for showing showing neutral neutral colour colour of Indicator pH = pKln pKln or[HIn] = [In – ] or [InOH] = [In+] Relation between between ionisation ionisati on constant (K i) & degree of ionisati ionisation( on(a):IONIC EQUILIBRIUM
a2 a2 C K i = = (Ostwald’ss (1 - a)V (1- a) dilution law) It is applicable to weak electrolytes for which a <<1 then
K i or V C ¯ a C Common ion effect : By addition of X mole/L of a common common ion, to a weak acid (or weak base) a becomes becomes equal to
a = K i V =
K a æ K b ö or ÷ [where a = degree of dissociation] X çè Xø (A) If solubility product > ionic product then the solution is unsaturated unsatur ated and more of the substance can be dissolved in it. (B) If ionic product > solubility product the solution is super saturated (principle of pr ecipitation). ecipitation). Salt of weak acid and strong base : K K pH = 0.5 0.5 (pK w + pK a + log c); h = ; K h = K a c (h = degree of hydrolysis) Salt of weak base and strong acid : K w pH = 0.5 0.5 (pK w – pK b – log c); h = K ´ c b Salt of weak acid and weak base :
pH = 0.5 0.5 (pK w + pK a – pK b ); h =
CHEMICAL KINETICS
Differences between order and molecularity molecularity of reaction: reaction:
Order of reaction
1. 2. 3. 4. 5.
K w K a ´ K b
It is experimentally determinedquantity Itcan hav have inte ntegral ral, frac ractio tional nal or or nega negattive ive values It ca canno nnot be be obtained from balanced or stoichiometric stoichiometric equation. equation. It tells tells about about the slowe slowest st ste step in the the mec mechani hanissm It is sum of the the pow powers of the conce ncentr ntrati ation term termss in therate ratelaw equation.
Molecularity
It is is a theoret retical co concept. Always integra gral values only nly, nev never ze zero or nega negattive ive It can be obtained. It does does not tell anything anything abo about me mechani hanissm It is the the num numbber of of re reacting ting species und undeergo rgoing simu simulltane taneoous collis llisiion in in the the reaction.
Unit of Rate constant :
k = mol1–n litn–1 sec –1 Order of reaction It can be fraction, zero or any an y whole number. number. Molecularity of reaction is always always a whole number. It is never more than three. th ree. It cannot be zero. First Order reaction :
a 2.303 0.693 log10 (a - x ) & t1/12 = t k [A]t = [A]0e –kt
k=
Second Order Reaction :
When concentration of A and B taking same.
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11 1 æ x ö k 2 = ç a (a x ) ÷ - ø t è When concentration of A and B are taking different 2.303 b(a - x) k 2 = t (a - b) log a ( b - x )
THERMODYNAMICS
Zero Order Reaction :
a 2k The rate of reaction is independent of the concentr ation of the reacting substance. Time of nth fraction of first order pr ocess, æ 1 ö 2×303 303 t 1/ n = log ç 1÷ k ç1 - ÷ x = kt &
P1 log P 2 Wrev ³ Wirr
t1/2 =
è
Arrhenius equation :
k = Ae –Ea/RT & slope =
-E a 2.303R
nø
& Temperature Coefficient
æ k 2 ö E a æ T2 - T1 ö ç ÷ log ç k ÷ = è 1 ø 2.303 è T1T2 ø It has been found that for a chemical reaction with rise in temperature by 10 °C, the rate constant gets nearly doubled. doubled. Oxidant itself is reduced (gives O2) ® e – (s) Acceptor Or Oxidant ¾¾ Reductant itself is oxidised (gives H2) OXIDATION ® e – (s) Donor Or reductant ¾¾ REDUCTION (i) Strongness of acid µ O.N O.N (ii) Strongness of base µ 1/ O.N (a) Electro Chemical Series:- Li, K, Ba, Sr, Ca, Na, Mg, Al, Mn, Zn, Cr, Fe, Cd, Co, Ni, Sn, Pb, Pb, H2, Cu, Ag, Pt, Au. (b) As we move from from top to bottom in this th is series (1) Standard Reduction Reduction Potential (2) Standard Oxidation Potential ¯ (3) Reducing Capacity ¯ (4) IP (5) Reactivity ¯ Equivalent weight of element element Atomicwt Atomicwt of theeleme theelement nt = Valenc Valencyy of elemen elementt VOLUMETRIC The law of Dulong and Petit ANALYSIS Atomic wt.×specific wt.×specific heat » 6.4 Normali Normality ty (N) number of equivalents = volume of the solution in litres number of moles Molarity (M) = volume of the solution in litres Common acid-base indicators Indicator
Methyl orange Methyl red Litmus Phenolphthalein
Acid colour Alkaline colour pH range of chan e
Red Red Red Colourless
Yellow Yellow Blue r ed
3.2–4.4 4.2–6.2 4.5–8.3 8.3–10
First Law : DE = Q + W Expression Expressi on for pressure volume work W = –PDV Maximum work in a reversible expansion : V2 W = –2.303n RT log V = –2.303 nRT T 1
qv = cvDT = DU, q p = c pDT = DH Enthapy changes during phase transformation (i) Enthalpy of Fusion (ii) Heat of Vapourisation (iii) Heat of Sublimation
Enthalpy : DH = DE + PDV = DE + DngRT Kirchoff’s equation equation : DET2 = DET1 + DCV (T2 – T1) [constant V]
DHT2 = DHT1 + DCP (T2 – T1) [constant P] Entropy(s) : Measure of disorder or randomness
DS = SS p – SSR
V2 P1 q ev = 2.303 nR log V = 2.303 n R log P T 1 2 Free energy change : DG = DH – TDS – DG = W(maximum) – PDV DH DS DG Reaction characteristics – + Alway Alwayss negative negative React Reaction ion is is spontane spontaneous ous at all temperature. + – Always po positive Reaction is is no nonspontaneous at all temperature – – Negative at low Spontaneous at low temp. & temp tempera eratur turee but but non non sponta spontaneo neous us at high high positive at high temperature temperature temperature + + Positive at low Non spontaneous at low temp. but temp. & spontaneous at high nega negati tivve at at high high temp. temperature
DS =
m = Z.I.t ELECTROCHEMISTRY
l eq
Degree of dissociation : a = l 0 = eq Equiva Equivalen lentt conduc conductanc tancee at given given concen concentrati tration on equiv equival alen entt cond conduct uctanc ancee at infinite infinite dilu dilution tion
1 S RA / l RA C 0 0 Kohlrausch’s law : L = x lA + yl 0B Nernst Equation Equation [Products] 0.0591 E = Eº – Eº – log10 [Reactants] n
Lsp =
1
Specific conductance l 1000 = ´ Lsp . ;L =
=
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12
é nEº ù & EºCell = Eºright + Eºleft & K eq. = antilog ê ë 0.0591úû DG = – nFEcell & DGº = –nFEº cell æ ¶DG ö & Wmax= +nFEº & DG = DH + T ç ¶T ÷ è øP Calculation of pH of an electrolyte by using a calomel E cell - 0.2415 electrode : pH = 0.0591 Thermodynamic efficiency of fuel cells :
Raoult’s law P = pA + pB = p°AXA + p°BXB
Characteristics Characteristic s of an ideal solution: solution: (i) DsolV = = 0 (ii) Dsol H = 0
=
Relative lowering lowering of vapour pressure o P – P A o P A
P Ao – PA P
o
= X B =
GASEOUS STATE
nB n A + nB
Colligative µ Number Number of particles particles properties µ Number of ions (in case of electrolyte electrolytes) s) µ Number of of moles of solute Depression of freezing point, DTf = K f m Elevation in boiling point p oint with relative lowering of vapour pressur e
Osmotic pressure (P) with depression in freezing point DTf dRT P = DTf ´ 1000K Relation between Osmotic pressure and other colligative properties: properties:
æ p oA - p A ö dRT ç ÷´ p = (i) Relativelowering of vapour pressure o ç ÷ è pA ø M B dRT (ii) p = DT b ´ Elevation in boiling boiling point 1000K b Elevation Depression in freezing point
Normal molar mass Observed Observed colligativ colligativee property property i= = Observe Observedd molar molar mass Normal colligative property
i =
Observed Observed osmotic osmotic pressure pressure Normal osmotic pressure
Degree of association association a = (1 – i)
n
n -1 i -1 & degree of dissociation (a) = n -1
8RT & Most probable speed sp eed = M Average speed = 0.9213 × RMS speed RMS speed = 1.085 × Average Average speed MPS = .816 × RMS; RMS = 1.224 MPS MPS : A.V. speed : RMS = 1 : 1.128 : 1.224 1 Rate of diffusion µ density of gas van der Waal’s equation
2RT M
æ n 2a ö ç P + 2 ÷ (V - nb) = nRT for n moles V ø è PV ; Z = 1 for ideal gas nRT Available space filled up by hard spheres (packing fraction):
Z (compressibility factor) =
SOLID AND LIQUID STATE STATE
Simple cubic = bcc = fcc =
hcp =
p 2
= 0.7 0.744
p 3 8
p 2 6
diam iamond =
p 6
= 0.52
= 0.68 = 0.74
p 3
= 0.34 6 6 Radius ratio and co-ordination number (CN)
Limiting radius ratio
CN
Geometry
[0.155– 0.225] [0.255–0.414] [0.414–0.732] [0.732–1]
3 4 6 8
[plane triangle] [tetrahedral] [octahedral] [bcc]
Atomic radius r and the edge of the unit cell: Pure elements : a 3a 2a ; bcc r = ; fcc = 2 4 4 Relationship between radius radiu s of void (r) and the radius ra dius of the sphere (R) : r (tetrahedral) = 0.225 R ; r (octahedral) = 0.414 R Paramagnetic : Presence Pr esence of unpaired electrons [attracted by magnetic field] Ferromagnetic : Permanent magnetism [ ] Antiferromagnetic : net magnetic moment is zero [ ¯ ¯] Ferrimagnetic : net magnetic moment is three [ ¯ ¯ ] Simple cubic = r =
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3RT = M
3P d
1000K b æ po - p ö DT b = ç ÷ M1 çè po ÷ø (M1 = mol. wt. of solvent)
dRT (iii) p = DTf ´ 1000K f
3PV = M
RMS velocity C =
Average speed =
o nFEcell -DG -nFE h= = DH DH For H2 –O2 fuel cells it is 95%.
SOLUTION AND COLLIGATIVE PROPERTIES
Ideal Idea l gas equation equa tion : PV = nRT (i) R = 0.0821 liter atm. at m. deg –1 mole –1 (ii) R = 2 cals. deg. –1 mole – (iii) R = 8.314 JK –1 mole –1 Velocities related to gaseous state
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SURFACE CHEMISTRY & COLLOIDAL STATE
Emulsion : Colloidal soln. of two immiscible immiscible liquids [O/W emulsion, W/O emulsion] Emulsifier : Long chain hydrocarbons are added to stabilize emulsion. Lyophilic Lyophiliccolloid: Starchygum,gelatin have greater affinity a ffinity for for solvent.
13 Lyophobic Lyophobic colloid : No affinity for solvent, solvent, special special methods are used to prepare sol. [e.g. As2S3, Fe(OH)3 sol] Preparation of colloidal solution : (i) Dispersion methods (ii) Condensation method. Properties of colloidal solution : (i) Tyndall Tyndall effect effect (ii) Brownian movement movement (iii) Coagulation (iv) Filtrability Filtra bility..
INORG INO RGANI ANIC C CHEMI CH EMISTR STRY Y
PERIODIC TABLE
General electronic configuration (of outer orbits) s-block ns1–2 p-block ns 2 np 1– 6 d-block (n–1)d1–10 ns1–2 f-block (n–2) f 1–14 s 2 p 6 d 10 (n – 1)s2 p6d0 or 1 ns 2 Pr (L To R) Gr (T toB)
Property atom atomic ic radius radius ¯ ionisation ionisation potential potential electro electronn affinity affinity electro electro negativ negativity ity ¯ metallic metallic character character or electropositive character ¯ (f) (f) alkali alkaline ne charac characte ter r of hydroxides (g) (g) acidic acidic charac character ter (i) reduc reducing ing prope property rty ¯ (j) oxidisi oxidising ng propert propertyy (k) (k) non metalli metallicc character character 1 1 IP µ Metallic µ Reducing charact character er Metallic character character (a) (b) (c) (c) (d) (d) (e) (e)
¯ ¯ ¯
¯ ¯ ¯
1 µ nuclear charge. size Second electron affinity is always a lways negative. Electron affinity of chlorine is greater th an fluorine (small atomic size). The first element of a group has similar properties with the second element of the next group. This is called diagonal relationship. The diagonal relationship disappears after IV group. Atomic radii : Li < Na < K < Rb < Cs Electronegativity : Li > Na > K > Rb > Cs First ionization potential : Li > Na > K > Rb > Cs s-BLOCK Melting point Li > Na > K > Rb > ELEMENTS Cs Colour of the flame Li - Red, Na Golden, K - Violet, Rb - Red, Cs Cs Blue, Ca - Brick red, Sr - Blood red, Ba-Apple green Rb and Cs show photoelec ph otoelectric tric effect. Stability of of hydrides : LiH > NaH > KH > RbH > CsH Basic nature of hydroxides : LiOH < NaOH < KOH < RbOH < CsOH Hydration energy : Li > Na > K > Rb > Cs Reducing character : Li > Cs > Rb > K > Na
EA µ
BORON FAMILY
Stability of +3 oxidation state : B > Al > Ga > In > Tl Stability of of +1 oxidation state : Ga < In < Tl Basic nature of the oxides and hydroxides : B < Al < Ga < In < Tl Relative strength of Lewis acid : BF3 < BCl3 < BBr 3 < BI BI3
Ionisation energy : B > Al < Ga > In < Tl Electronegativity Electronegativity : Electronegativity Electronegativity first decreases from B to
Al and then increases marginally margin ally..
Reactivity Reactivity : C < Si < Ge < Sn < Pb Metallic character : C < Si < Ge < Sn < Pb Acidic character of the oxides : CARBON CO 2 > SiO2 > GeO2 > SnO2 > PbO2 FAMILY Weaker acidic (amphoteric) Reducing nature of hydrides CH4 < SiH4 < GeH4 < SnH4 < PbH4 Thermal stability of tetrahalides CCl4 > SiCl4 > GeCl4 > SnCl4 > PbCl4 Oxidising character of M+4 species GeCl4 < SnCl4 < PbCl4 Ease of hydrolysis of tetrahalides SiCl4 < GeCl4 < SnCl4 < PbCl4 Acidic strength of trioxides tr ioxides : N2O3 > P2O3 > As2O3 Acidic strength of pentoxides N2O5 > P2O5 > As2O5 > Sb2O5 > NITROGEN Bi2O5 Acidic strength of oxides of FAMILY nitrogen N2O < NO < N2O3 < N2O4 < N2O5 Basic nature, bond angle, thermal stability and dipole moment of hydrides NH3 > PH3 > AsH3 > SbH3 > BiH3 Stability of trihalides of nitrogen : NF3 > NCl 3 > NBr 3 Lewis Lewis base base strength strength : NF3 < NCl3> NBr 3 < NI3 Ease of hydrolysis of trichlorides NCl3 > PCl3 > AsCl3 > SbCl3 > BiCl3 Lewis acid strength of trihalides of P, As and Sb PCl3 > AsCl3 > SbCl3 Lewis acid strength among phosphorus ph osphorus trihalides PF3 > PCl3 > PBr 3 > PI PI3 Nitrogen displays displays a great tendency to form form pp – pp multiple bonds with with itself as well well as with with carbon and oxygen. oxygen. The basic strength of the hydrides NH3 > PH3 > AsH3 > SbH3
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14
The thermal therma l stability of the hydrides decreases as the atomic size increases. Melting and boiling point of hydrides H2O > H2Te > H2Se > H2S Volatility of hydrides H2O < H2Te < H2Se < H2S OXYGEN Reducing nature of hydrides FAMILY H2S < H2Se < H2Te Covalent character of hydrides H2O < H2S < H2Se < H2Te The acidic character of oxides (elements in the same oxidation state) SO2 > SeO2 > TeO2 > PoO2 ; SO3 > SeO3 > TeO3 Acidic character of oxide of a particular element (e.g. S) SO < SO2 < SO3 ; SO SO2 > TeO2 > SeO2 > PoO2 Bond energy of halogens : Cl2 > Br 2 > F2 > I2 Solubility of halogen in water : F2 > Cl2 > Br 2 > I2 Oxidising power : F2 > Cl2 > Br 2 > I2 Enthalpy of hydration of X – ion : F – > Cl – > Br – > I – Reactivity of halogens : F > Cl > Br > I Ionic character of M - X bond in halides M – F > M – Cl > M – Br > M – I Reducing character of X – ion : I – > Br – > Cl – > F – Acidic strength of halogen acids : HI > HBr > HCl > HF Conjugate base strength of halogen acids I – < Br – < Cl – < F – Reducing property of hydrogen halides HF < HCl < HBr < HI Oxidising power p ower of oxides oxides of chlorine Cl2O > ClO2 > Cl2O6 > Cl Cl2O7 Acidic character of oxyacids of chlorine HClO < HClO2 < HClO3 < HClO4 Oxidising power of oxyacids of chlorine HClO > HClO2 > HClO3 > HClO4 The element with exceptional configuration are Cr 24[Ar] 3d54s1, Cu29[Ar] 3d104s1 Mo 42 [Kr] 4d 5 5s 1 , Pd 46 [Kr] 4d10 5s 0 TRANSITION Ag 47 [Kr] 4d 10 5s 1 , Pt 78 [Xe] ELEMENTS 4f 145d 106s 0 Ferromagnetic substances are (d- and f-BLOCK those in which there are large ELEMENTS number of electrons with unpaired spins and whose magnetic moments are aligned in the same direction. HALOGEN FAMILY
Inner Transition Elements
(i) Electronic Configuration - The general electronic configuration configuration of these th ese elements is 4f 0 -14 5d [ Xe ] 4f
0 -1
6s2
(iii) Magnetic properties - Magnetic properties have spin and orbit contributions (Contrast “spin only”of transition metals). Hence magnetic momentums are given by the formula. m = 4 S ( S + 1) + L( L + 1)
Coordination number is the th e number of the nearest atoms or groups in the coordination sphere. Ligand is a Lewis base donor of COORDINATION electrons that bonds to a central metal COMPOUNDS atom in a coordination compound. Paramagnetic Paramagne tic substance is one one that is attracted to the magnetic field, this results r esults on account of unpaired electrons present in the atom/molecule/ion. Effective atomic number EAN = (Z – Oxidation number) + (2 × Coordination number) Factors affecting stability of complex (i) Greater the charge on the central metal ion, ion, greater is the th e stability. (ii) Greater the th e ability of of the ligand to donate electron pair (basic strength) greater g reater is the stability. (iii) Formation of chelate rings ring s increases the stability. stability. Isomerism in coordination compounds : (i ) (ii i ) (v) (vii) (ix) (x)
Structu ral Isomers (ii) Io I oniza tion Isomers Hydration Isomers (iv ) Li Linkage Isomers Coor Coordi dina nattion ion Iso Isomeri merism sm (vi) vi) Liga Ligand nd isom isomer eriism Polymeri Polymerisat sation ion Isomeri Isomerism sm (vii (viii) i) Valenc alencee Iso Isome meri rism sm Coordin Coordinatio ation n posi position tion isomeris isomerism m Stere tereo o is isomer omeris ism m (a) Geometrical (I) Squar Squaree plana planarr comple complexes xes of of the type type
MA2X2 ; MABX2 ; MABXY (II) Octahedral of the type : MA4XY, MA4X2 MA3X3 MA2X2Y2. M(AA)2X2 and M(ABCDEF). (b) (b) Opti Optica call isom isomeri erism sm The order of decreasing electronegativity of of hybrid orbitals is sp > sp2 > sp3. Conformational isomers are those isomers which arise due to rotation GOC GO C around a single bond. A meso compound is optically inactive, even though it has asymmetric centres (due to internal compensation of rotation of plane polarised light) An equimolar mixture of enantiomers is called racemic mixture, mixtur e, which is optically inactive. Reaction intermediates and reagents : Homolytic fission ® Free radicals Heterolytic Heterolytic fission ® ions (Carbonium, ion carbonium, etc.) Nucleophiles Nucleophiles – electron rich Two Two types : 1. Anions Anions 2. Neutral molecules with lone pair of electrons (Lewis bases) bases) Electrophiles : electron deficient. Two types : 1. Cations 2. Neutral molecules with vacant orbitals (Lewis acids). Inductive effect is due to s electron displacement along a chain and is perman ent effect. effect. +I (inductive effect) increases basicity, – I effect increases acidity of compounds. Resonance is a phenomenon in which two or more structures can be written for the same compound but none of them actually exists.
where L = Orbital quantum number, S = Spin quantum qua ntum number number Buy book bookss : http://www.dishapublication.com/entrance-exams-books/engineering-exams.html
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15
ORGA OR GANIC NIC CHEMI STR STRY Y Pyrolytic cracking is a process in which alkane decomposes to a mixture of smaller hydrocarbons, when it is heated strongly, in the absence of oxygen. Ethane can exist in an infinite number of conformations. They are
ALKANES
HH
H
H H H
H H H
H H
HH
H
H
H q = 60° Staggered
Eclipsed
q <
H
H
60° > 0 Skew
Conformations of Cyclohexane : It exists in two nonplanar,
strainless forms, the boat and the chair form
The order of reactivity is (a) RI > RBr > RCl > RF (b) Allyl halide > Alkyl halide > Vinyl Vinyl HALOGEN halide COMPOUNDS (c) Alkyl Alkyl halide hali de > Aryl halide S N1 reaction : Mainly 3° alkyl halides undergo this reaction and form racemic mixture. S N1 is favoured by polar solvent and low concentration of nucleophile. S N 2 reaction : Mainly 1° alkyl halides undergo this substitution. Walden Walden inversion takes place. S N2 reaction is preferred by non-polar solvents and high concentration of nucleophile. Reaction with metals:
(i)
Dry ether ether ¾® R – Mg – X R – X + Mg ¾¾¾ Alkyl alides
Grignard reagent
(ii) Wurtz reaction: Chair form Most Stable
R – X + 2 Na + X – R
Half Chair
Dry ether ether ¾¾ ¾ ¾® R - R + 2 N a + X – Alkane
Alkenes are converted to alcohol in different ways as follows Reagent Types Types of of addition
ALCOHOLS Twist Boat
Boat form (Least Stable)
In dehydration and dehydrohalogenation the preferential order for removal of hydrogen is 3° > 2° > 1° (Saytzeff’s rule). ALKENES The lower the D Hh (heat of hydrogenation) the more stable the alkene is. Alkenes undergo anti-Markonikov addition only with HBr in the presence of peroxides. Alkynes add water molecule in presence of mercuric mercur ic sulphate and dil. H2SO4 and form carbonyl compounds. compounds. Terminal alkynes have acidic H-atoms, ALKYNES so they form metal alkynides with Na, ammonical cuprous chloride solution and ammoniacal silver nitrate solution. Alkynes are acidic because of H-atoms which which are attac attached hed to sp ‘C’ atom atom which hich (a) has more more electronegativity (b) has more ‘s’ character than sp2 and a nd sp3 ‘C’ atoms. All o and p-directing groups are ring activating groups (except – X) They are : – OH, – NH2, – X, – R, – OR, etc. ARENES All m-directing groups are ring deactivating groups. They are : – CHO, – COOH, – NO2, – +
dil H2SO4 – Markovnikov Markovnikov B2H6 and H2O2, OH – – Anti-Markovnikov Oxymercuration demercuration –
Markovnikov Oxidation of 1° alcohol ¾¾ ¾ ¾ ® aldehyde ¾ ® carboxylic acid (with same no. (with same no. of of C atom) C atom) 2° alcohol ¾¾ car boxylic lic acid ® ketone ¾¾ ® carboxy (with same no. (with less no. of of C atom) C atom) 3° alcohol ¾¾ ® ketone ¾¾ ® carboxylic acid (with less no. (with less no. of of C atom) C atom) Q
CHCl3 / OH OH Phenol ¾¾¾¾ ¾¾ ¾¾ ¾¾ ® Phenolic aldehyde
PHENOLS
(Reimer-Tieman reaction) Phenol
CO2 ¾¾ ® Phenolic carboxylic carboxylic
D
acid (Kolbe reaction) Acidity of phenols (a) Increase by electron withdrawing substituents like – NO NO2, – CN, – CHO, – COOH, –X, - N R 3 (b) decrease by electron electron releasing substituents like – R, R, – OH, – NH2, – NR 2, – OR
CN, – NR 3 , etc. Buy book bookss : http://www.dishapublication.com/entrance-exams-books/engineering-exams.html www.chementor.weebly.com www.chementor.weebl y.com
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16 Al2O3 2ROH ¾¾¾¾ ® R - O - R + H 2O 250ºC
®ROR '+ NaX RONa + X - R ' ¾¾ ETHERS
(Williamson's synthesis) synthesis) dil. H SO
¾4¾® 2ROH ROR + H 2 O ¾¾¾2 ¾¾ D
Formation of alcohols using RMgX (a) Formaldehyde Formaldeh yde + RMgX RMgX
CARBONYL COMPOUNDS
Hydrolysis ¾¾¾ ¾¾ ® 1° alcohol Hydrolysis (b) Aldehyde + RMgX ¾¾¾¾¾ ¾¾ ¾¾¾ ® 2° alcohol (other than HCHO) HCHO)
(c) Ketone + RMgX
Hydrolysis ¾¾ ¾¾ ®
3° alcohol Cannizzaro reaction (Disproportionation) Hot conc. conc. ¾¾¾¾ ® Alcohol + Salt of acid Aldehyde ¾¾¾¾® alkali
(no a H-atom) Aldol condensation : Carbonyl compound compound + dil. alkali –– ® b-hydroxy carbonyl (with a H H-atom) compound Benzoin condensation ethanolic Benzaldehyde ¾¾¾¾ ¾¾¾ ¾® Benzoin NaCN
The relative reactivities r eactivities of different different acid derivatives derivat ives towards towards nucleophilic acyl substitution reactions follow the order: O O O O O || || || || || R – C – Cl > R – C – O – C – R ' > R – C – OR ' > R – C – NH NH2 Acid chloride
Anhydride
Ester
Amide
Carbohydrates are polyhydroxy aldehydes or ketones. Monosaccharides are simple sugars, CARBOHYDRATES, containing three to nine carbon atoms. AMINO ACIDS AND Characteristic reactions : Homologous series POLYMERS Type of reactions (a) Alkanes Substitution (Mostly free radical (b) (b) Alke Alkene ness and and alky alkyne ness Elec Electr trop ophi hill llic ic addi additi tioon (c) Arenes Electroph illic s ubstitution (d) Alkyl halides Nucleophillic substitution (e) (e) Aldehy Aldehyde de and keto ketones nes Nucle Nucleoph ophil illi licc addit additio ionn Tests to differentiate : 1°, 2° and 3° alcohols (1) Lucas test (2) Victormeyer’s test 1°, 2° and 3° amines Hinsberg test 1°, 2° and 3° nitro compounds Test with HNO2 and KOH Aryl halides and alkyl halides Test with AgNO 3 solution Alde Aldehy hyde dess and keto ketone ness Tollen’ len’ss test/F st/Feehli hling’ ng’s test Arom Aromat atic ic alde aldehy hyde dess and and Fehli hling’ ng’s test Aliphatic aldehydes Dil H2SO4 [or Conc. H2SO4 + H2O] Use ® Hydrating agent (+HOH) Alc. KOH or NaNH2(Use ® -HX) alc.KOH CH3CH2Cl ¾¾¾¾ ® CH2=CH2 Lucas reagent ZnCl 2 + Conc. HCl Use ® for distinction between 1º, 2º & 3º alc. Tilden Reagent NOCl (Nitrosyl chloride) NOCl C2H5 NH2 ¾¾¾ ® C2H5Cl Alkaline KMnO4(Strong oxidant) Toluene ® Benzoic acid Bayer’s Regent : 1% alkaline KMnO 4(Weak oxidant) Use: ® For test of > C = C < or –C = C –
IMPORTANT REAGENT
BR CH2=CH2+H2O+[O] ¾¾® ¾¾ ® CH2OH–CH2OH [O]
Acidic K 2Cr 2O7 (Strong oxidant) : RCH2OH ¾® ¾® RCHO The rate of esterfication decreases n SnCl2/HCl or Sn/HCl use ® for red of nitrobenzene in acidic when alcohol, acid or both have medium. branched substituents. SnCl 2 / H Cl Cl Ortho effect : All ortho ¾¾¾¾ ¾ ® C6H5 NH2 C6H5 NO2 ¾¾¾¾¾ CARBOXYLIC 6H substituted benzoic acids (irrespective ACIDS Lindlar’s Catalyst = Pd/CaCO 3 of type of of substituent) are str onger than + in small quantity (CH 3COO)2Pb benzoic acid. " 2 – butye + H2 ¾¾ ® Cis-2-butene Order Order of basic basicity ity : (R = – CH3 or (main product) – C2H5) Ziegler –Natta Catalyst (C 2H5)3Al + TiCl 4 2° > 1° > 3° > NH3 Use In Addition polymerisation Hofmann degradation NITROGEN IDENTIFICATION TESTS : (a) Unsaturated compound (Bayer’s reagent) B r / KO K O H COMPOUNDS 2 Amides ¾¾¾¾® 1° amine Decolourising the reagent (b) Alcohols (Ceric ammonium nitrate solution) The basicity of amines is Red colouration (a) decreased by electron electron withdrawing withdrawin g (c) Phenols (Neutral FeCl 3 solution) groups Violet/deep blue colouration (b) increased by electron releasing groups (d) Aldehydes and ketones (2, 4-D.N.P.) Reduction of nitrobenzene nitr obenzene in different media gives different Orange precipitate precipitate products produ cts (e) Acids (NaHCO 3 solution) Medium
Product
Acidic Basic sic Neutral Neutral
Aniline Azo Azoxy, xy, Azo Azo and and fin final ally ly hydr hydraz azoobenze nzene Phenyl hydroxylamine hydroxylamine
Brisk effervescence (CO 2 is evolved) (f) 1° amine (CHCl 3 + KOH) Foul smell (isocyanide) (g) 2° amine (NaNO 2 + HCl) Yellow oily liquid (Nitrosoamine)
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