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Primary alcohols are those alcohols where the carbon atom of the hydroxyl group (OH) is attached to only one single alkyl group. Some examples of these primary alcohols include Methanol (propanol), ethanol, etc.
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Secondary alcohols are those where the carbon atom of the hydroxyl group is attached to two alkyl groups on either side. The two alkyl groups present may be either structurally identical or even different.
Tertiary alcohols feature a hydroxyl group attached to the carbon atom, which is connected to 3- alkyl groups. The presence of this -OH group allows the alcohols to form hydrogen bonds with their neighbouring atoms.
Hand sanitizer or the alcohol based rub are consumer products in the form of liquid or gel and are thought to generally be effective at killing microorganisms and decreasing infectious agents on our hands. While there are a variety of hand sanitizers available, they can be classified into two major groups: non-alcohol and alcohol-based sanitizers. While non-alcohol based sanitizers may contain surfactants like benzalkonium chloride or antimicrobial agent like triclosan, alcohol-based versions typically contain some combination of isopropyl alcohol, ethanol (ethyl alcohol), and/or n-propanol. The alcohol-based sanitizers are typically the most popular and the versions that contain 60 to 95% alcohol are most effective. Some versions of alcohol based sanitizers contain compounds such as Glycerine/glycerol (a trihydric alcohol) as a moisturizing component to prevent drying of the skin.
Since the major components of alcohol-based hand sanitizers includes lower alcohols like methanol, ethanol, n-propanol and iso-propanol that are quite volatile, the prime testing method is performed using gas chromatography (GC). In GC, the volatile compounds of interest are primarily separated based on boiling point and GC columns with polar selectivity provide additional intermolecular interaction like dipole interaction to separate individual components based on polarity. A quick look at the analyte shows that the compounds of interest here has hydroxyl -OH group (alcohol group).
Like-dissolves-like is the principle of gas chromatography and hence a polar column selectivity like ZebronTM ZB-WAXplus is an excellent choice to separate the alcohols of interest far from each other. ZB-WAXplus is a Polyethyleneglycol based GC column with a polarity number of 52. This GC stationary phase, unlike traditional PEG phase can handle 100% aqueous sample in addition to providing polar selectivity. As represented in Figure 1 (App:15817), alcohol compounds including methanol, ethanol, propanol and butanol are separated within 15 minutes from the aqueous matrix. In addition to the separation, injection to injection reproducibility can be noticed for this challenging aqueous matrix. This high throughput separation example employed sample with a high percentage ethanol to mimic alcohol based sanitizer. A run time of less than 15 minutes is extremely helpful for faster testing and expedited batch release based on the GC test results.
In addition to lower alcohols, trihydric alcohols such as glycerols are added as moisturizer in hand sanitizers. Figure 2 (App: 16510) shows the separation of some of the common glycol and glycerols that are added to sanitizers. Here as well, a run time as short as 10 minutes helps provide high-throughput separation.
Alcohols and phenols are formed when a hydrogen atom is in a hydrocarbon, aliphatic and aromatic respectively, which is replaced by the -OH group. These classes of compounds have a wide application in different industries as well as in day-to-day life. In this article, you will learn about the preparation of alcohols through various methods.
An alcohol contains one or more hydroxyl groups (-OH) directly attached to a carbon atom of an aliphatic system. Alcohols can be classified as monohydric, dihydric, trihydric and polyhydric compounds, depending if they contain 1,2,3 or multiple hydroxyl groups attached to the carbon atom in a compound.
Preparation of alcohols by hydroboration oxidation in which diborane \((BH_3)_2\) reacts with alkenes to give trialkyl boranes as an additional product, which is further oxidised to alcohol by hydrogen peroxide in presence of aqueous NaOH.
An aldehyde group is reduced to the corresponding alcohols by adding hydrogen in presence of catalysts. It is also treated by sodium borohydride or lithium aluminium hydride as aldehydes yield primary and secondary alcohols.
Preparation of alcohols is possible by the reaction of Grignard reagents with aldehydes and ketones. It is the nucleophilic addition of Grignard reagent to the carbonyl group to form an adduct and hydrolysis of this adduct yield alcohol, as represented by the mechanism given below.
The surface tension data of the alcohols used in the present work is from references [7] and [8]. Thermo chemical data is from reference [9]. Other physical constants like density, molecular weight and boiling points are from standard sources.
Here it is worth to discuss about the boiling points of the alcohols. The boiling point of 1-propanol (97C) is greater than that of propane (-43C) (Table 1) in spite of the two molecules have the same number of electrons and almost the same shape. The prime reason is that primary alcohols can form hydrogen bonds between two molecules (intermolecular) (scheme 1). In the case of secondary alcohols one would have to compare the boiling point of 2-propanol (83C) and propane again (-43C) (Table 1). The boiling point of the secondary alcohol is less than that of the corresponding primary alcohol with the same number of carbon atoms. Though the boiling point of 2-propanol is less than that of 1-propanol in spite of their ability to form inter-molecular hydrogen bonding, they have only one hydrogen atom on the oxygen and the oxygen in secondary alcohol is in the middle of the two carbon atoms makes the dipole-dipole interactions less than in 1-propanol in which oxygen is at the end in the molecule whose dipole-dipole interactions are strong enough. Hence lower boiling points in secondary alcohols compared to the corresponding primary alcohols. The same arguments hold good for 1,2 and 1,3-propanediols where in 1,3-propanediol the two hydroxyl groups are on the terminal carbons makes it high boiling with high degree of dipole-dipole interaction. In the case of glycerol, though it had same number of carbons but the boiling point is too high 290C. The reason for this we have attributed that glycerol is a non-ionic kosmotrope (order-maker) that forms strong hydrogen bonds with neighbouring molecules, resulting in larger molecular aggregates [13]. This is again reflected on the largest hydrogen donor-acceptor ((Had) value of glycerol (Table 1). This may lead glycerol to have high boiling point.
5.3.5. The compositions according to the US-document comprise from about 1% to about 30% by weight of at least one co-solvent (claim 1, compound (c)). These co-solvents aid in removing dried paint, stabilizing the composition, and moisturizing the skin (column 3, lines 5 and 6). Different compounds are envisaged for this purpose, namely monohydric alcohols having from 1 to 22 carbon atoms, dihydric and polyhydric alcohols having from 2 to 22 carbon atoms, polyethylene glycols and polypropylene glycols having molecular weights of from 100 to 20,000; and also esters of aliphatic monobasic and dibasic acids having from 2 to 22 carbon atoms (column 2, line 52 to column 3, line 4). However, only propylene glycol and ethanol are exemplified as co- solvents (Example I). 041b061a72