Wine is no longer a stranger to us, but how it is structured and has its properties is not known to everyone. So the following article provides chemical information related to alcohol for readers.
1. What is alcohol?
Alcohol, also known as alcohol, is an organic compound in which one or more hydroxyl groups (-OH) are directly bonded to the saturated carbon atom of the hydrocarbon radical.
General formula: R – OH.
Where: R is a hydrocarbon: can be saturated or not
For example: ONLY3OH, C2H5OH, ONLY3ONLY2ONLY2OH, ONLY2=CHON2OH, C6H5ONLY2OH…
2. Properties of Alcohol:
2.1. Physical properties:
R-OH forms hydrogen bonds, so the boiling point of alcohols is higher than that of hydrocarbon derivatives of equivalent molecular mass. Below is the order of decreasing boiling point of some groups of organic compounds:
R-COOH > R-OH > RNR’ > R-COO-R’ > R-CO-R’> R-CHO > RX > RO-R’ > RH
equivalent
Acids > alcohols > amines > esters > ketones > aldehydes > halogen derivatives > ethers > hydrocarbon CxHy
Explanation: the boiling point of a substance usually depends on the following factors:
The larger the molecular mass, the higher the boiling point.
– Polarity of the bond: ionic bond > polar covalent bond > nonpolar covalent bond.
Number of hydrogen bonds: the more hydrogen bonds, the higher the boiling point.
– Strength of hydrogen bonds: the stronger the H bond, the higher the boiling point.
The solubility of alcohol depends on the number of C atoms in the molecule:
C1-C3: well soluble in water
C4-C7: partially soluble in water
C8 and above: insoluble in water
From C1 to C12 alcohol is a liquid, from C13 and above alcohol is a solid.
2.2. Chemical properties:
2.2.1. Alcohols react with alkali metals (Alcol + Na):
Alcohol + Na . Reaction
R(OH)z + zNa → R(ONa)z +z/2H2↑
Alcohol almost does not react with NaOH, but on the contrary, sodium alcohol is completely decomposed
R(ONa)z + zH2O → R(OH)z + zNaOH
Attention: In the reaction of alcohols with Na:
mNa increase = malcohol – mH2 = nalcohol.(CODE)CHEAP + 16z).
malcohol bottle increase = mNa – mH2 = nalcohol.22z.
– If an alcohol solution is reacted with Na, in addition to the reaction of alcohol, there is also a reaction of H .2O with Na.
– Number of alcohol functional groups = 2.nH2/nalcohol.
2.2.2. Alcohols react with acids:
a) Alcohol reacts with inorganic acid HX (Alcol + H2SO4Alcohol + HCl)
OLDnH2n+2-2k-z(OH)z + (z + k)HX → CnH2n + 2 – zXz + k
b) Alcohols react with organic acids (esterification reaction)
ROH + R’COOH R’COOR + H2O
yR(OH)x + xR'(COOH)y R’x(COO)xyCHEAPy + xyH2O
Attention:
The reaction is carried out in an acidic medium and heated.
– The reaction is reversible, so pay attention to the equilibrium shift.
2.2.3. Water splitting reaction (dehydration):
a) Extract water from an alcohol molecule to form an alkene of a saturated, monofunctional, open-chain alcohol.
OLDnH2n+1OH → CnH2n + FRIENDS2O (HOT)2SO4 solid, >1700C)
– Conditions of alcohol participating in the reaction: alcohol has Hα.
Attention:
– If an alcohol is saturated, an open-chain monomer does not split water to form an alkene, then that alcohol does not have Hα (it is only Hα).3OH or alcohol where the C atom is bonded to the OH only bonded to another tertiary C).
– If an alcohol splits water to give a mixture of many alkenes, it is a higher order alcohol (second order, tertiary) and the C chain is asymmetric through C bonded to OH.
– Many alcohols split water to form an alkene, the following possibilities occur:
There are alcohols that do not separate from water.
Alcohols are isomers of each other.
– The main product in the process of water separation according to Zaixep rule.
– When solving exercises related to the water splitting reaction, remember:
malcohol = malkenes + mH2O + mResidual alcohol
nalcohol reacts = nalkenes = nwater
Special dehydration reactions:
ONLY2OH-ONLY2OH → ONLY3FOR + THEM2O
ONLY2OH-CHOH-JUST2OH → ONLY2=CH-FOR + 2FUL2O
b) Splitting water from 2 alcohol molecules to form ethers
ROH + ROH → ROR + H2O (HOT)2SO4 solid; 1400C)
ROH + R’OH → ROR’ + H2O (HOT)2SO4 solid; 1400C)
Attention:
– From n different alcohols when separating water, we get n.(n + 1)/2 ethers in which n ethers are symmetrical.
– If water is separated to yield ethers with the same number of moles, the alcohols participating in the reaction also have the same number of moles and nalcohol = 2.nether = 2.nH2O and nalcohol = mether + nH2O + mResidual alcohol.
2.2.4. Oxidation reaction (Alcol + O2):
a) Complete oxidation
OLDxHyOz + (x + y/4 – z/2)O2 → xCO2 + y/2H2O
Attention:
– The combustion reaction of alcohols has similar characteristics to the corresponding hydrocarbon combustion reaction.
+ If alcohol is burned, it gives nH2O > nCO2 → alcohol that is burned is saturated alcohol and nalcohol = nH2O – nCO2.
+ If alcohol is burned, it gives nH2O > 1.5.nCO2 → alcohol is ONLY3OH. ONLY4 and ONLY3OH has this property (excluding amines).
– When an organic compound X is burned, n . is foundH2O > nCO2 → the substance is an alkane, an open-chain saturated alcohol or an open-chain saturated ether (with the same formula CnH2n+2Ox).
b) Incomplete oxidation (Alcol + CuO or O2 catalyst is Cu)
– Primary alcohol + CuO to form aldehydes:
RCH2OH + CuO → RCHO + Cu + H2O
– Secondary alcohol + CuO to form ketones:
RCHOHR’ + CuO → RCOR’ + Cu + H2O
– Tertiary alcohols are not oxidized by CuO.
Attention: msolids reduce = mCuO react – mCu create = 16.nalcohol unit.
2.2.5. Specific reactions of some alcohols:
a) Ethyl alcohol ONLY3ONLY2OH:
OLD2H5OH + O2 → ONLY3COOH + HOW2O (vinegar yeast)
2 C2H5OH → ONLY2=CH-CH=ONLY2 + 2 HOUSES2O + H2 (Al2O3ZnO, 4500C)
b) Unsaturated alcohols react like corresponding hydrocarbons
– Reaction with Hydrogen, allylicium ONLY2 = CH – ONLY2OH: Alcohol + H2
ONLY2=CH-ONLY2OH + H2 → ONLY3– ONLY2– ONLY2OH (Ni, t0)
– Reaction with Bromine: Alcohol + Br2
ONLY2=CH-ONLY2OH + Br2 → ONLY2Br-CHBr-ONLY2OH
– Reaction with potassium permanganate: Alcohol + KMnO4
3 ONLY2=CH-ONLY2OH + 2KMnO4 + 4 HOURS2O → 3C3H5(OH)3 + 2KOH + 2MnO2
c) Polyfunctional alcohol with adjacent OH groups: give a blue solution with Cu(OH)2 At normal temperature:
2R(OH)2 + Cu(OH)2 → [R(OH)O]2Cu + 2H2O
d) Some cases of unstable alcohols:
Alcohols with an OH group bonded to a C double bond are transformed into aldehydes or ketones:
ONLY2=CH-OH → ONLY3GIVE
ONLY2=COH-ONLY3 → ONLY3-CO-ONLY3
– Alcohols with 2 OH groups attached to 1 C atom are separated to form aldehydes or ketones:
RCH(OH)2 → RCHO + Surname2O
HO-CO-OH → HO2O + CO2
RC(OH)2R’ → RCOR’ + OR2O
Alcohols with 3 OH groups attached to 1 C atom are separated from water to form acids:
RC(OH)3 → RCOOH + HIM2O
3. Alcohol classification:
Based on the characteristics of the hydrocarbon radical, alcohols are divided into:
– Alcohol no.
– Unsaturated alcohol. – Aromatic alcohol (molecular with benzene ring).
Based on the number of –OH groups in the molecule, alcohols are divided into:
– Monofunctional alcohol.
– Multifunctional alcohol.
Alcohols are also classified according to the alcohol degree
a) Saturated alcohol, monofunctional, open circuit:
The molecule has an –OH group attached to an alkyl radical.
CnH2n+1-OH or CnH2n+2O ( n ≥ 1)
For example: CH3-OH, C2H5-OH, …
b) Unsaturated alcohol, monofunctional, open circuit:
The molecule has an –OH group attached to the saturated carbon atom of the unsaturated hydrocarbon radical.
Example: CH2=CH-CH2-OH
SURE-CH2-OH
*Unsaturated alcohol, single bonded, monofunctional, open circuit:
Example: CH2=CH-CH2-OH
CH2=CH-CH2-CH2-OH
CH2=CH-CH2-CH2-CH2-OH
CnH2n1OH (n≥3)
c) Aromatic alcohol, monofunctional:
A molecule with an –OH group attached to a saturated carbon atom in the branch chain of the benzene ring.
d) Saturated, monocyclic alcohol:
The molecule has an –OH group attached to a saturated carbon atom of a saturated hydrocarbon radical.
e) Multifunctional alcohol:
Molecule with two or more –OH alcohol groups.
Example: Ethylene glycol, glycerol
* Saturated alcohol, multifunctional: CnH2n+2Ox or CnH2n+2x(OH)x (n≥ 3)
* Classification according to the order of alcohols: The order of alcohols is calculated by the order of the saturated carbon atom
bound to the –OH group.
The degree of a saturated carbon atom is calculated by the number of bonds that carbon atom has with other carbon atoms.
4. Alcohol preparation and application:
4.1. Integrated approach:
a) Prepare the alcohol from the corresponding alkene:
– In industry synthesizing ethanol from ethylene.
It is also possible to synthesize alcohols by hydrolysis of halogen derivatives in alkaline solution.
b) Synthesis of glycerol from propylene:
4.2. Application:
– Methanol Mainly used to produce Andehit Formic raw material for plastics industry.
– Ethanol Used to prepare some organic compounds such as acetic acid, diethyl ether, ethyl acetate… Due to its good solubility in some organic compounds, Ethanol is used to mix varnishes, pharmaceuticals, perfumes… In daily life, Ethanol is used to prepare beverages with different alcohol levels.
5. How to recognize alcohol:
There are several ways to identify alcohol:
Alcohol reacts with alkali metals to form a colorless gas.
Wine will turn from black to red when heated.
– If the compound is a polyfunctional alcohol containing an adjacent oh group, then cu(oh) 2 will dissolve to give a blue solution.
If the compound is an unsaturated alcohol, the reaction will discolor the bromine solution.
6. Illustrated exercise:
Form 1: Water-separated alcohol
Post first: Boil 132.8 grams of a mixture of 3 saturated and monotonic alcohols with H2SO4 solid at 140oC yields a mixture of ethers with the same number of moles and a mass of 111.2 grams. What is the number of moles of each ether in the mixture?
A. 0.1 mol.
B. 0.15 mol.
C. 0.4 mol.
D. 0.2 mol.
Solution guide
We know that for every 3 alcohols that separate under the H . condition2SO4 solid, 140oC forms 6 ethers and separates 6 H . molecules2O.
According to the CLC, we have
mH2O = malcohol – mether = 132.8 – 111.2 = 21.6g
nH2O = 1.2 mol = nether
neach ether = 1.2/6 = 0.2 mol Answer
Form 2: Alcohol reacts with Na
For 13.8 grams of alcohol A react with excess Na to release 5.04 liters H2 in dktc, know USA < 100. So A has a reduced structural formula:
A. ONLY3OH.
B. OLD2H5OH.
C. OLD3H6(OH)2.
D. OLD3H5(OH)3.
Solution guide
Let the formula of the alcohol be R(OH)n.
Reaction Equation:
2R(OH)n + 2Na → 2R(ONa)n + n2 (first)
13.8/(R+17n) →
13.8/(R+17n). n/2 (mol)
According to (1) and assuming we have: nH2 = 13.8/(R+17n). n/2 = 0.225 mol
⇒ R = 41/3n ⇒ n = 3; R = 41
So A has a reduced structural formula of C .3H5(OH)3
ANSWER EASY
Form 3: Alcohol is oxidized incompletely
Put mg of a saturated alcohol (alcohol), X through a flask of CuO (excess), and heat it. After the reaction is complete, the mass of solids in the flask is reduced by 0.32 grams. The resulting vapor mixture has a mass density for hydrogen of 15.5. What is the value of m?
Solution guide
Let the molecular formula of alcohol saturated, unit X be : CnH2n + 2O
Reaction Equation:
OLDnH2n + 2O + CuO → CnH2nO + H2O + Cu (1)
x x → x → x → x (mol)
mc/r decrease = mCuO – mCu = 80x – 64x = 0.32 => x = 0.02
Vapor mixture of CnH2nO and H2O has M=15.5.2 = 31 and n = 0.02.2 = 0.04 mol.
Applying the law of conservation of mass we have:
malcohol = msteam mixture + mCu – mCuO
malcohol = 0.04.31 + 0.02.64 – 0.02.80 = 0.92 grams
